drm/display/dp_mst: Fix down message handling after a packet reception error

drm/display/dp_mst: Fix down message handling after a packet reception error

commit 1241aedb6b5c7a5a8ad73e5eb3a41cfe18a3e00e upstream.

After an error during receiving a packet for a multi-packet DP MST
sideband message, the state tracking which packets have been received
already is not reset. This prevents the reception of subsequent down
messages (due to the pending message not yet completed with an
end-of-message-transfer packet).

Fix the above by resetting the reception state after a packet error.

Cc: Lyude Paul <lyude@redhat.com>
Cc: <stable@vger.kernel.org> # v3.17+
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221214184258.2869417-2-imre.deak@intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>