drm/amd/display: Fix missing DCE check in dm_gpureset_toggle_interrupts()

drm/amd/display: Fix missing DCE check in dm_gpureset_toggle_interrupts()

This line was lost when cping from amd-staging-drm-next to drm-fixes.
So add it back.

Cc: stable@vger.kernel.org
Fixes: 8382cd234981 ("drm/amd/display: consolidate DCN vblank/flip handling onto vupdate_no_lock")
Reported-by: Lu Yao <yaolu@kylinos.cn>
Signed-off-by: Leo Li <sunpeng.li@amd.com>
Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>
Link: https://patch.msgid.link/20260723134450.13838-1-sunpeng.li@amd.com
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>