Move instantiation of msgbufp from 9 MD files to subr_prf.c.

This variable should be pure MI except possibly for reading it in MD
dump routines.  Its initialization was pure MD in 4.4BSD, but FreeBSD
changed this in r36441 in 1998.  There were many imperfections in
r36441.  This commit fixes only a small one, to simplify fixing the
others 1 arch at a time.  (r47678 added support for
special/early/multiple message buffer initialization which I want in
a more general form, but this was too fragile to use because hacking
on the msgbufp global corrupted it, and was only used for 5 hours in
-current...)

sys/amd64/amd64/machdep.c

@@ -184,8 +184,6 @@ struct init_ops init_ops = {
  */
 extern char kernphys[];
 
-struct msgbuf *msgbufp;
-
 /*
  * Physical address of the EFI System Table. Stashed from the metadata hints
  * passed into the kernel and used by the EFI code to call runtime services.

sys/arm/arm/pmap-v4.c

@@ -265,8 +265,6 @@ void		(*pmap_copy_page_offs_func)(vm_paddr_t a_phys,
 		    int cnt);
 void		(*pmap_zero_page_func)(vm_paddr_t, int, int);
 
-struct msgbuf *msgbufp = NULL;
-
 /*
  * Crashdump maps.
  */

sys/arm/arm/pmap-v6.c

@@ -294,8 +294,6 @@ vm_paddr_t first_managed_pa;
  */
 caddr_t _tmppt = 0;
 
-struct msgbuf *msgbufp = NULL; /* XXX move it to machdep.c */
-
 /*
  *  Crashdump maps.
  */

sys/arm64/arm64/pmap.c

@@ -221,8 +221,6 @@ vm_offset_t virtual_avail;	/* VA of first avail page (after kernel bss) */
 vm_offset_t virtual_end;	/* VA of last avail page (end of kernel AS) */
 vm_offset_t kernel_vm_end = 0;
 
-struct msgbuf *msgbufp = NULL;
-
 /*
  * Data for the pv entry allocation mechanism.
  * Updates to pv_invl_gen are protected by the pv_list_locks[]

sys/i386/i386/pmap.c

@@ -255,7 +255,6 @@ pt_entry_t *CMAP3;
 static pd_entry_t *KPTD;
 caddr_t ptvmmap = 0;
 caddr_t CADDR3;
-struct msgbuf *msgbufp = NULL;
 
 /*
  * Crashdump maps.

sys/kern/subr_prf.c

@@ -122,6 +122,7 @@ static void  snprintf_func(int ch, void *arg);
 
 static int msgbufmapped;		/* Set when safe to use msgbuf */
 int msgbuftrigger;
+struct msgbuf *msgbufp;
 
 static int log_console_output = 1;
 SYSCTL_INT(_kern, OID_AUTO, log_console_output, CTLFLAG_RWTUN,

sys/mips/mips/machdep.c

@@ -318,8 +318,6 @@ cpu_initclocks(void)
 	cpu_initclocks_bsp();
 }
 
-struct msgbuf *msgbufp = NULL;
-
 /*
  * Initialize the hardware exception vectors, and the jump table used to
  * call locore cache and TLB management functions, based on the kind

sys/powerpc/powerpc/pmap_dispatch.c

@@ -72,7 +72,6 @@ static struct kobj_ops	mmu_kernel_kops;
  */
 struct pmap kernel_pmap_store;
 
-struct msgbuf *msgbufp;
 vm_offset_t    msgbuf_phys;
 
 vm_offset_t kernel_vm_end;

sys/riscv/riscv/pmap.c

@@ -220,8 +220,6 @@ vm_offset_t virtual_avail;	/* VA of first avail page (after kernel bss) */
 vm_offset_t virtual_end;	/* VA of last avail page (end of kernel AS) */
 vm_offset_t kernel_vm_end = 0;
 
-struct msgbuf *msgbufp = NULL;
-
 vm_paddr_t dmap_phys_base;	/* The start of the dmap region */
 vm_paddr_t dmap_phys_max;	/* The limit of the dmap region */
 vm_offset_t dmap_max_addr;	/* The virtual address limit of the dmap */

sys/sparc64/sparc64/pmap.c

@@ -99,11 +99,6 @@ __FBSDID("$FreeBSD$");
 #include <machine/tsb.h>
 #include <machine/ver.h>
 
-/*
- * Virtual address of message buffer
- */
-struct msgbuf *msgbufp;
-
 /*
  * Map of physical memory reagions
  */