The MCxx values must be based off memory clock, not CPU core clock.

This also fixes the bug where on some machines the LCD went crazy
while using PCMCIA.
Signed-off-by: Marek Vasut <marek.vasut@gmail.com>
Cc: Nicolas Pitre <nico@fluxnic.net>
Reviewed-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Eric Miao <eric.y.miao@gmail.com>