As part of decommissioning mips support, remove the boot loader
support. Do this in advance of other boot loader work to limit the
amount of work that will be thrown away.
Sponsored by: Netflix
Reviewed by: jrtc27
Differential Revision: https://reviews.freebsd.org/D33377
Clean up libstand zalloc* sources. Note that it is not 100% whitespace cleanup.
I also reduced block in znalloc and zfree as those were obvious simplifications
and did help to save one level of indent.