drm/i915/mtl: Support HBR3 rate with C10 phy and eDP in MTL

eDP specification supports HBR3 link rate since v1.4a. Moreover,
C10 phy can support HBR3 link rate for both DP and eDP. Therefore,
do not clamp the supported rates for eDP at 6.75Gbps.

Cc: <stable@vger.kernel.org>

BSpec: 70073 74224

Signed-off-by: Chaitanya Kumar Borah <chaitanya.kumar.borah@intel.com>
Reviewed-by: Mika Kahola <mika.kahola@intel.com>
Signed-off-by: Mika Kahola <mika.kahola@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231018113622.2761997-1-chaitanya.kumar.borah@intel.com