ps3fb: Update for firmware 2.10

ps3fb: Update for firmware 2.10

As of PS3 firmware version 2.10, the GPU command buffer size must be at least 2
MiB large. Since we use only a small part of the GPU command buffer and don't
want to waste precious XDR memory, move the GPU command buffer back to the
start of the XDR memory reserved for ps3fb and let the unused part overlap with
the actual frame buffer.

Signed-off-by: Geert Uytterhoeven <Geert.Uytterhoeven@sonycom.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>