First of all we should not be looking at fb->{width,height} as those do
not tell us what the actual pipe size is. Second of all we need to use
>= for the comparison.

So fix the comparison, and make use of the new pipe_src_{w,h} to
determine the real pipe source dimensions.
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>