drm/i915: Lift runtime-pm acquire callbacks out of intel_wakeref.mutex

drm/i915: Lift runtime-pm acquire callbacks out of intel_wakeref.mutex

When runtime pm is first woken, it will synchronously call the
registered callbacks for the device. These callbacks
may pull in their own forest of locks, which we do not want to
conflate with the intel_wakeref.mutex. A second minor benefit to
reducing the coverage of the mutex, is that it will reduce
contention for frequent sleeps and wakes (such as when being used
for soft-rc6).

v2: remove usage of fetch_and_zero() and other improvements(Jani)

Signed-off-by: Chris Wilson <chris.p.wilson@intel.com>
Signed-off-by: Nirmoy Das <nirmoy.das@intel.com>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230926083742.14740-2-nirmoy.das@intel.com