SM501: initialise SDRAM clock before bus clocks

This init sequence of setting the SDRAM clock before the bus clock is
recommend by Silicon Motion to stop problems with writes not sticking into
registers.

Signed-off-by: Vincent Sanders <vince@simtec.co.uk>
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>