drm/dp_mst: Verify request type in the corresponding down message reply

After receiving the response for an MST down request message, the
response should be accepted/parsed only if the response type matches
that of the request. Ensure this by checking if the request type code
stored both in the request and the reply match, dropping the reply in
case of a mismatch.

This fixes the topology detection for an MST hub, as described in the
Closes link below, where the hub sends an incorrect reply message after
a CLEAR_PAYLOAD_TABLE -> LINK_ADDRESS down request message sequence.

Cc: Lyude Paul <lyude@redhat.com>
Cc: <stable@vger.kernel.org>
Closes: drm/i915/kernel#12804


Reviewed-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241203160223.2926014-3-imre.deak@intel.com