video: ARM CLCD: fix up Integrator support

We need to mask all registers of the Integrator/CP core module
control register, and actually write the calculated value to the
control register, not the mask.

Tested on the Integrator/CP with RGB5551 VGA and works like a
charm after this patch.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>