drm/amd/display: Check correct bounds for stream encoder instances for DCN303

drm/amd/display: Check correct bounds for stream encoder instances for DCN303

commit 89b008222c2bf21e50219725caed31590edfd9d1 upstream.

[Why & How]
eng_id for DCN303 cannot be more than 1, since we have only two
instances of stream encoders.

Check the correct boundary condition for engine ID for DCN303 prevent
the potential out of bounds access.

Fixes: cd6d421e3d1a ("drm/amd/display: Initial DC support for Beige Goby")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: stable@vger.kernel.org
Reviewed-by: Chris Park <Chris.Park@amd.com>
Reviewed-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Acked-by: Tom Chung <chiahsuan.chung@amd.com>
Signed-off-by: Aurabindo Pillai <aurabindo.pillai@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>