drm: Add link training repeaters addresses

drm: Add link training repeaters addresses

DP 1.3 specification introduces the Link Training-tunable PHY Repeater,
and DP 1.4* supplemented it with new features. In the 1.4a spec, it was
introduced some innovations to make handy to add support for systems
with Thunderbolt or other repeater devices.

It is important to highlight that DP specification had some updates from
1.3 through 1.4a. In particular, DP 1.4 defines Repeater_FEC_CAPABILITY
at the address 0xf0004, and DP 1.4a redefined the address 0xf0004 to
DP_MAX_LANE_COUNT_PHY_REPEATER.

Changes since V4:
- Update commit message
- Fix misleading comments related to the spec version
Changes since V3:
- Replace spaces by tabs
Changes since V2:
- Drop the kernel-doc comment
- Reorder LTTPR according to register offset
Changes since V1:
- Adjusts registers names to be aligned with spec and the rest of the
  file
- Update spec comment from 1.4 to 1.4a

Cc: Abdoulaye Berthe <Abdoulaye.Berthe@amd.com>
Cc: Harry Wentland <harry.wentland@amd.com>
Cc: Leo Li <sunpeng.li@amd.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Manasi Navare <manasi.d.navare@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Abdoulaye Berthe <Abdoulaye.Berthe@amd.com>
Reviewed-by: Harry Wentland <Harry.Wentland@amd.com>
Signed-off-by: Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190909212144.deeomlsqihwg4l3y@outlook.office365.com