drm/i915/dp: Handle a tunneling IRQ after acking it

drm/i915/dp: Handle a tunneling IRQ after acking it

HPD IRQs in general should be handled after acking them. The

1. Read IRQ register (read DP_DEVICE_SERVICE_IRQ_VECTOR,
   DP_LINK_SERVICE_IRQ_VECTOR_ESI0)
2. Handle IRQ
3. Ack IRQ (write DP_DEVICE_SERVICE_IRQ_VECTOR,
   DP_LINK_SERVICE_IRQ_VECTOR_ESI0)

sequence would miss a new interrupt triggered after 2. and before 3.,
since the flag set in the IRQ register for this interrupt would be
cleared in step 3.

Fix the above by handling the IRQ after acking it.

Reviewed-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patch.msgid.link/20260225164618.1261368-5-imre.deak@intel.com