With this change, it is now possible to verify the pin function and level
of reserved pins (but not set them).
The use of reserved pins on Raspberry pi can lead to short circuits and
real damage to the SoC.
While here, remove duplicated code, make use of OF_getencprop_alloc()
instead of using fixed sized variables and reduce the dmesg spam by
printing reserved pin ranges (when possible) instead of printing each pin
in the range.
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