arm: Fix compilation error in m5 utility

Changeset 5ca6098b9560 accidentally broke the m5 utility. This
changeset adds the missing co-processor call used to trigger the
pseudo-op in ARM mode and fixes an alignment issue that caused some
pseudo-ops to leave thumb mode.
arm: Make libm5 a dependency of the m5 utility

The m5 utility wasn't relinked properly since libm5.a wasn't a
dependency of the utility. This changeset addresses that issue.
arm: Add support for the m5fail pseudo-op