sh: Merge the legacy PMB mapping and entry synchronization code.

This merges the code for iterating over the legacy PMB mappings and the
code for synchronizing software state with the hardware mappings. There's
really no reason to do the same iteration twice, and this also buys us
the legacy entry logging facility for the dynamic PMB case.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>