Fix image and color handling in atyfb_cursor()

- In the 2-bit scheme of the cursor image, just set the first bit to be
  always zero (turn off transparency and/or XOR), and just do the masking
  manually

- The cursor color is converted into 32-bit RGBA8888 using struct fb_cmap.
  Each component in the cmap is u16 in size, so mask the upper 8 bits.
Signed-off-by: Antonino Daplas <adaplas@pol.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>