savagefb: rework i2c bit access

Use already defined VGAwCR/VGArCR functions to access the i2c bus.

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>