[PATCH] fbdev: riva warning fix

drivers/video/riva/fbdev.c: In function `riva_get_EDID_OF':
drivers/video/riva/fbdev.c:1846: warning: assignment discards qualifiers from pointer target type

This code is being bad: copying a pointer to read-only OF data into a
non-const pointer.

Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: "Antonino A. Daplas" <adaplas@pol.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>