stand: Avoid unaligned access in smbios code

[imp]

Summary

This code was written on x86 where unaligned accesses were
easy. However, in some environments fault on unaligned access, so use
memcpy instead of dereferencing unaligned pointers.

Sponsored by: Netflix

[diizzy]

stand/libsa/smbios.c

100

unalgined --> unaligned

[imp]

Better comments on why we use memcpy, also add a note this data is LE, so add
the leXtoh macros for it, though they will be no-ops on all FreeBSD's supported
platforms.