drm/i915/selftests: Fix compare functions provided for sorting

Both cmp_u32 and cmp_u64 are comparing the pointers instead of the value
at those pointers. This will result in incorrect/unsorted list. Fix it
by deferencing the pointers before comparison.

Fixes: 4ba74e53 ("drm/i915/selftests: Verify frequency scaling with RPS")
Fixes: 8757797f

 ("drm/i915/selftests: Repeat the rps clock frequency measurement")
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20200709154931.23310-1-sudeep.holla@arm.com
(cherry picked from commit 2196dfea

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