SM501: Fix sm501_init_reg() mask/set order

The order of the set and mask operation in sm501_init_reg() was setting and
then masking the bits set.  Correct the order so that we do not end up with
288MHz SDRAM clocks on certain systems.

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>