fbdev: sh_mobile_lcdc: Don't acknowlege interrupts unintentionally

The LDINTR register caries both interrupt enable and interrupt status
bits. When setting or clearing interrupt enable bits, write all status
bits to 1 to avoid acknowledging interrupts by mistake.

When acknowledging interrupts, write 1 to all non-triggered interrupt
bits to avoid losing interrupts.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>