Don't include <sys/clist.h> inside ucom(4) and ufoma(4).

After being ported to the MPSAFE TTY layer, these drivers do not use
clists anymore. Don't include their header files.

sys/dev/usb/ucom.c

@@ -78,7 +78,6 @@ __FBSDID("$FreeBSD$");
 #include <sys/conf.h>
 #include <sys/serial.h>
 #include <sys/tty.h>
-#include <sys/clist.h>
 #include <sys/file.h>
 #include <sys/selinfo.h>
 #include <sys/proc.h>

sys/dev/usb/ufoma.c

@@ -88,7 +88,6 @@ __FBSDID("$FreeBSD$");
 #include <sys/conf.h>
 #include <sys/serial.h>
 #include <sys/tty.h>
-#include <sys/clist.h>
 #include <sys/file.h>
 #include <sys/select.h>
 #include <sys/sysctl.h>