pvr2fb: Consolidated cleanup of pvr2fb.c

pvr2fb: Consolidated cleanup of pvr2fb.c

- better handling of the pvr2 registers based on more up to date information.

Testing shows that it seems to work pretty well at 16bpp, 24bpp and 32bpp -
including proper rendering of the boot logo at all levels (previously this was
a bit broken even at 16bpp) and giving white against black text.  Really
detailed testing (eg with X11) requires support for the maple bus - which
isn't (currently - next project assuming this is okay) available, but I have
no reason to think this is broken.

Signed-off by: Adrian McMenamin <adrian@mcmen.demon.co.uk>
Acked-by: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Antonino Daplas <adaplas@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>