[PATCH] ARM: Fix AMBA CLCD fb driver for 32bpp

We were supporting 24bpp.  However, the pixel organisation in
memory was 0RGB, so it was 24bpp in 32bit words.  This means
we're actually supporting 32bpp and not 24bpp.

Also, add a check to ensure that we don't exceed the available
framebuffer when changing display resolutions.

Signed-off-by: Russell King <rmk@arm.linux.org.uk>