There's no need to export the internal PMB functions for allocating,
freeing and modifying PMB entries, etc. This way we can restrict the
interface for PMB.

Also remove the static from pmb_init() so that we have more freedom in
setting up the initial PMB entries and turning on MMU 32bit mode.
Signed-off-by: NMatt Fleming <matt@console-pimps.org>
Signed-off-by: NPaul Mundt <lethal@linux-sh.org>