hwc: do not allow gsc downscaling by exactly max_downscale

The Gscaler registers do not have enough bits to represent downscaling
by exactly 16x

Bug: 10946861

Change-Id: I6a9921193d9188bca2344815c29863c550c5e3dd
Signed-off-by: Greg Hackmann <ghackmann@google.com>
1 file changed