drm/i915/dg2: fix snps buf trans for uhbr

The UHBR check was using > instead of >=. Use the helper instead to
avoid mistakes. Also always use the non-UHBR values for HDMI.

v2: Use intel_crtc_has_dp_encoder() && intel_dp_is_uhbr() (Ville)

Fixes: 2817efae ("drm/i915/dg2: add SNPS PHY translations for UHBR link rates")
Reported-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211007124201.18686-1-jani.nikula@intel.com