drm/i915/dp: Ack only the handled device service IRQs

drm/i915/dp: Ack only the handled device service IRQs

Only those IRQs should be acked that are handled, however for SST all
IRQs triggered by the sink are acked. This can be a problem for flags
that are reserved/reading zero at a given moment, but become used for
some purpose - with a side-effect if set - in a future DPCD revision.

Fix the above by acking only those device service IRQs that will be
handled. While at it add asserts that only the known/acked device
service IRQs are handled both in the MST and SST case.

Reviewed-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patch.msgid.link/20260225164618.1261368-20-imre.deak@intel.com