matroxfb: Clean-up i2c header inclusions

matroxfb_crtc2 has nothing to do with i2c, so there's no reason why
matroxfb_crtc2.h should include i2c header files.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Acked-by: Petr Vandrovec <vandrove@vc.cvut.cz>