Rather than poking at the smemc registers directly from the
pcmcia/pxa2xx_base driver, move those bits into machine file
to have a cleaner interface.

Cc: Dominik Brodowski <linux@dominikbrodowski.net>
Link: https://lore.kernel.org/lkml/87d0egjzxk.fsf@belgarion.home/Signed-off-by: Arnd Bergmann <arnd@arndb.de>