drm/nouveau/disp: fix DP capable DSM connectors

Just special case DP DSM connectors until we properly figure out how to
deal with this.

This resolves user regressions on GPUs with such connectors without
reverting the original fix.

Cc: Lyude Paul <lyude@redhat.com>
Cc: stable@vger.kernel.org # 6.4+
Closes: https://gitlab.freedesktop.org/drm/nouveau/-/issues/255
Fixes: 2b5d1c29

 ("drm/nouveau/disp: PIOR DP uses GPIO for HPD, not PMGR AUX interrupts")
Signed-off-by: Karol Herbst <kherbst@redhat.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231011114134.861818-1-kherbst@redhat.com