drm/i915/psr: Modify intel_dp_get_su_granularity to support panel replay

drm/i915/psr: Modify intel_dp_get_su_granularity to support panel replay

Currently intel_dp_get_su_granularity doesn't support panel replay.
This fix modifies it to support panel replay as well.

v4:
  - use drm_dp_dpcd_readb instead of drm_dp_dpcd_read
  - ensure return value is 0 if drm_dp_dpcd_readb fails
v3: use correct offset for DP_PANEL_PANEL_REPLAY_CAPABILITY
v2: rely on PSR definitions on common bits

Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
Reviewed-by: Animesh Manna <animesh.manna@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240510093823.3146455-8-jouni.hogander@intel.com