This fixes some bugs in the gxt4500 framebuffer driver, and adds support
for GXT6000P cards.

First, I had the red and blue channels swapped in the colormap update code,
resulting in penguins' noses and feet turning blue (though the penguins
weren't actually shivering :).

Secondly, the code that calculated the values to put in the PLL that
generates the pixel clock wasn't observing some constraints that I wasn't
originally aware of, but am now that I have some documentation on the chip.

The GXT6000P is essentially identical from software's point of view, except
for a different reference clock for the PLL, and the addition of a geometry
engine (which this driver doesn't use).

Signed-off-by: Paul Mackerras <paulus@samba.org>
Cc: James Simmons <jsimmons@infradead.org>
Cc: "Antonino A. Daplas" <adaplas@pol.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>