Update nvme(4) and nvd(4) man pages to clarify the differences between
their respective device nodes.

Sponsored by:	Intel
MFC after:	3 days
Trim at EOL.

MFC after:	3 days
It is not uncommon for BIOSes to report wrong RMRR entries in DMAR
table.  Among them, some (old AMI ?) BIOSes report entries with range
like (bf7ec000, bf7ebfff).  Attempts to ignore the bogus entries
result in faults, so the range must be covered somehow.

Provide a workaround by identity mapping the 32 pages after the bogus
entry start, which seems to be enough for the reported BIOS.

Reported and tested by:	Jason Harmening <jason.harmening@gmail.com>
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week