nvidiafb: Fix reversed DDC port

nvidiafb: Fix reversed DDC port

After I added some debugging printks I've found that code became a bit
confused because it believed that primary monitor is 1920x540, but later it
found in CRTC0's registers that panel size is 1920x1200 (Windows also agree
that 1920x1200 is primary monitor, and 1920x1080i secondary one).

When I applied attached patch then my monitor became as happy as it was
before I connected HDMI cable to secondary output.

Signed-off-by: Petr Vandrovec <vandrove@vc.cvut.cz>
Signed-off-by: Antonino Daplas <adaplas@gmail.com>
Cc: Dave Airlie <airlied@linux.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>