drm/i915/pmdemand: Use the default 2 usec fast polling timeout

drm/i915/pmdemand: Use the default 2 usec fast polling timeout

For whatever unknown reason the pmdemand code is using a custom
50 usec fast polling timeout instead of the normal 2 usec
value. Switch to the standard value to get rid of the special
case.

The eventual aim is to get rid of the fast vs. slow timeout
entirely and switch over to poll_timeout_us().

Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patch.msgid.link/20251106152049.21115-11-ville.syrjala@linux.intel.com