drm/i915: Treat DMRRS as static DRRS

Some machines declare DRRS type = seamless, DRRS = no, DMRRS = yes.
I *think* DMRRS stands for "dynamcic media refresh rate", and
I suspect the way it's meant to work is that it lets the driver
switch refresh rates to match the frame rate for media playback.
Obviously for us all that kind of policy stuff is entirely up to
userspace, so the only thing we may do is make the extra refresh
rate(s) available.

So let's treat this case as just static DRRS for now. In the
future We might want to differentiate the "seamless w/ downclocking"
vs. "seamless w/o downclocking" cases so that we could do seamless
refresh rate changes for systems that only claim to support DMRRS.

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/125


Acked-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220531191844.11313-7-ville.syrjala@linux.intel.com