drm/dp: Add HBR3 support in existing DRM DP helpers

Existing helpers add support upto HBR2. This patch
adds support for HBR3 rate (8.1 Gbps) introduced as
part of DP 1.4 specification.

Change-Id: I6a3e50b2e148c6fae103afc73bb51e4b93e72a5c
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1516660991-20697-1-git-send-email-manasi.d.navare@intel.com
[cohens@codeaurora.org: resolve trivial conflict with downstream change]
Git-commit: e0bd878a959008f02a1280b1dd2c128324586af3
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: Steve Cohen <cohens@codeaurora.org>