drm/i915/icl: Define TA_TIMING_PARAM registers

This patch defines DSI_TA_TIMING_PARAM and
DPHY_TA_TIMING_PARAM registers used in
dphy programming.

v2: Changes (Jani N)
    - Define mask/shift for bitfields
    - Use bitfields name as per BSPEC
    - Define remaining bitfields

Signed-off-by: Madhav Chauhan <madhav.chauhan@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1537095223-5184-8-git-send-email-madhav.chauhan@intel.com