drm/i915: Don't try to use DDR DVFS on CHV when disabled in the BIOS

drm/i915: Don't try to use DDR DVFS on CHV when disabled in the BIOS

If one disables DDR DVFS in the BIOS, Punit will apparently ignores
all DDR DVFS request. Currently we assume that DDR DVFS is always
operational, which leads to errors in dmesg when the DDR DVFS requests
time out.

Fix the problem by gently prodding Punit during driver load to find out
whether it will respond to DDR DVFS requests. If the request times out,
we assume that DDR DVFS has been permanenly disabled in the BIOS and
no longer perster the Punit about it.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=91629
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Clint Taylor <Clinton.A.Taylor@intel.com>
Tested-by: Clint Taylor <Clinton.A.Taylor@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>