rivafb/nvidiafb: Various cleanups

Various cleanups to rivafb/nvidiafb's I2C code:
* Drop useless par->bus.
* Refactor I2C bus deletion code.
* Drop useless variable initialization.
* Remove unneeded include of <linux/i2c-id.h>.
* Simplify +1/-1.
* Add __devinit tags where possible.

[adaplas]
The varible initialization are not useless. However, rivafb must
check if i2c bus are created properly before reading the EDID
block.

Signed-off-by: Jean Delvare <khali@linux-fr.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>