Now our binutils's assembler supports the Intel Random Number Generator
extensions, we can change the .byte directives in sys/dev/random/ivy.c
to plain 'rdrand' mnemonics.  This already worked for clang users, but
now it will also work for gcc users.

Approved by:	re (kib)
Approved by:	so (des)
MFC after:	1 week
After r256062, the static function fbsdrun_get_next_cpu() in
usr.sbin/bhyve/bhyverun.c is no longer used, so remove it to silence a
gcc warning.

Approved by:	re (glebius)