drm/xe/pmu: Get/put runtime pm on event init

drm/xe/pmu: Get/put runtime pm on event init

When the event is created, make sure runtime pm is taken and later put:
in order to read an event counter the GPU needs to remain accessible and
doing a get/put during perf's read is not possible it's holding a
raw_spinlock.

Suggested-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250124050411.2189060-4-lucas.demarchi@intel.com
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>