During phy compliance auto test mode source need to read
requested test pattern from sink through DPCD. After processing
the request source need to set the pattern. So set/get method
added in drm layer as it is DP protocol.

v2: As per review feedback from Manasi on RFC version,
- added dp revision as function argument in set_phy_pattern api.
- used int for link_rate and u8 for lane_count to align with existing code.

v3: As per review feedback from Harry,
- used sizeof() instead of magic number.
- corrected kernel-doc for drm_dp_phy_test_params structure.
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Manasi Navare <manasi.d.navare@intel.com>
Signed-off-by: Animesh Manna <animesh.manna@intel.com>
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200316103759.12867-3-animesh.manna@intel.com