drm/i915/display: Extend DP HDR support to hsw+

HSW+ platforms are able to send out HDR Metadata SDP DIP
packet as GMP. Hence, extending the support for HDR on DP
encoders for the same.

v2: Limited to non eDP ports on hsw/bdw and removed it for
lspcon as it is done separately (suggested by Ville)

v3: Added helper and limited eDP restriction to port A (Ville)

v4: Dropped some redundant checks (Ville)

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/5389
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Uma Shankar <uma.shankar@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220324120438.1876445-1-uma.shankar@intel.com