drm/i915/gt: Sanitize RPS interrupts upon resume

Currently we clear and disable the RPS pm interrupts on module load, and
presume that they remain disabled forevermore. However, the mask is
cleared on suspend and so after resume they may start showing up again
unexepectedly.

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/1811
Fixes: 8e99299a

 ("drm/i915/gt: Track use of RPS interrupts in flags")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Andi Shyti <andi@etezian.org>
Reviewed-by: Andi Shyti <andi@etezian.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200502173512.32353-1-chris@chris-wilson.co.uk