Store persistent reservation keys as uint64_t instead of uint8_t[8].

This allows to simplify the code and save 512KB of RAM per LUN (8%)
by removing no longer needed "registered" keys flags.
Use FreeBSD-bit-checking-style
This appease gcc 4.9 issuing warnings about parentheses

Differential Revision:	https://reviews.freebsd.org/D933
Reviewed by:	marius
Fix typo revealed by using newer binutils

Differential Revision:	https://reviews.freebsd.org/D933
Reviewed by:	marius
o Add machine-dependent SMP part
o Enable SMP

Sponsored by:	DARPA, AFRL