drm/amd/display: Handle Y carry-over in VCP X.Y calculation

commit 71956473 upstream.

Theoretically rare corner case where ceil(Y) results in rounding up to
an integer. If this happens, the 1 should be carried over to the X
value.

CC: stable@vger.kernel.org
Reviewed-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: George Shen <george.shen@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>