MFC r335027, r335050

r335027:
When this code was introduced at r300829 the author forgot to add
the BSD license header that is the same as in its C header file.

Sponsored by: iXsystems Inc.

r335050:
While I was investigating CID 1194192 related with a resource leak on mrp memory
allocation, I could identify that actually we use this pointer on pci_emul.c as
well as on vga.c source file.

I have reworked the logic here to make it more readable and also add a warn to
explicit show the function where the memory allocation error could happen,
also sort headers.

Also CID 1194192 was marked as "Intentional".

Obtained from: TrueOS
Sponsored by: iXsystems Inc.