mfd: sm501 fix gpio number calculation for upper bank

The sm501_gpio_pin2nr() routine returns the wrong values for gpios in the
upper bank.

Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>