ARMv7-A: stop using CP15 ops

ARMv7-A: stop using CP15 ops

The ARMv7-A code uses read_cp15() to access fault registers.
Instead, use DPM operations directly, passing in the relevant
MRC instructions.

This eliminates per-operation overhead (though it'll be hard
to observe, this is uncommon) and helps eliminate read_cp15().

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>