drm/i915/dp: Track pm_qos per connector

Since multiple connectors may run intel_dp_aux_xfer conncurrently, a
single global pm_qos does not suffice. (One connector may disable the
dma-latency boost prematurely while the second is still depending on
it.) Instead of a single global pm_qos, track the pm_qos request for
each intel_dp.

v2: Move the pm_qos setup/teardown to intel_dp_aux_init/fini

Fixes: 9ee32fea

 ("drm/i915: irq-drive the dp aux communication")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Imre Deak <imre.deak@intel.com>
Reviewed-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201230202309.23982-1-chris@chris-wilson.co.uk
(cherry picked from commit b3304591

)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>