drm/i915/display: Compute has_drrs after compute has_psr

DRRS and PSR can't be enable together, so giving preference to PSR
as it allows more power-savings by complete shutting down display,
so to guarantee this, it should compute DRRS state after compute PSR.

Cc: Srinivas K <srinivasx.k@intel.com>
Cc: Hariom Pandey <hariom.pandey@intel.com>
Reviewed-by: Anshuman Gupta <anshuman.gupta@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200825171331.17971-1-jose.souza@intel.com