Fix MP_LOCKDEBUG and add back the tick counter if we spin too much on
mpl.

MP_LOCKDEBUG had a wrong comparison due to the newer ticket locks.

ok patrick@
Add ethernet support to the Utilite.

Unfortunately the MAC address is stored in an i2c eeprom,
so we'll have to use a randomly generated one for now.

ok drahn@
Use the u-area for the undefined stack in our machdep code.

Also kill FP context.

ok drahn@
Use %p instead of 0x%x, spotted by patrick.

ok patrick@
use queue.h macros in buf_get() and buf_put()

use queue.h macros in buf_get() and buf_put() instead of accessing
fields by name; no binary change
Allow for cross builds of ld.so.

Do not evaluate the if ld.so can be run if HOSTCC != CC
Arm needs __clear_cache, so provide it.
repair error check for failed 'mount -ur' on ffs

repair check for ffs_flushfiles() failure when updating a busy file
system to read-only, which got broken in commit 8051e527 by yours truly.

rant: ffs_mount() code is horrific when it comes to mount updates.
Move loadaddr on i.MX6 to a safer place.

"yes!" drahn@
Expose clock frequencies via sysctl using sensors framework.
mount -ur/uw support for tmpfs

allow tmpfs to be made read-only from read-write, and vice-versa.
switch bread_cluster() to b_private

b_saveaddr is meant to be physio-only
put b_saveaddr and b_private under a union

both fields are mutually exclusive; b_saveaddr is used only in the
physio path, and b_private for clustered reads or wapbl flushes.

combined with the removal of b_synctime, this allows us to allocate one
more buf per page on amd64, and two on i386.
Really test for USR mode before enabling VFP.

ok drahn@