drm/i915/selftest: Change throttle criteria for rps

Current live_rps_control() implementation errors out on throttling.
This was done with the assumption that throttling to minimum frequency
is a catastrophic failure, which is incorrect. Throttling can happen
due to variety of reasons and often times out of our control. Also,
the resulting frequency can be at any given point below the maximum
allowed. Change throttle criteria to reflect this logic and drop the
error, as it doesn't necessarily mean selftest failure.

Signed-off-by: Raag Jadav <raag.jadav@intel.com>
Reviewed-by: Vinay Belgaumkar <vinay.belgaumkar@intel.com>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Acked-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20250102110618.174415-1-raag.jadav@intel.com