[PATCH] fbdev: nvidiafb: Driver cleanup

- remove redundant casts
- add mode_option to module parameter

Signed-off-by: Antonino Daplas <adaplas@pol.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>