staging: gma500: get control from firmware framebuffer if conflicts

Many Linux distributions would enable vesafb in order to display
early stage boot splash. In this case, we will get garbled X
Window screen if running X fbdev on psbfb.

This is because fb0 is occupied by vesafb while psbfb is on fb1.
They tried to drive the same pieces of hardware at the same
time. With unmodified X start-up, it would try to use default
fb0 framebuffer device and unfortunately it is now broken
becaues fb1 supersedes it.

We should let psbfb takeover framebuffer control from vesafb
to get around this problem.

See also commit : 4410f391

Signed-off-by: Michael Chang <mchang@novell.com>
Cc: Alan Cox <alan@linux.intel.com>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>