drm/i915/tgl: Add mipi dsi support for TGL

Most of the functions and mipi dsi sequence remains
same as of ICL for TGL. Hence extending the support
to TGL.

Signed-off-by: Vandita Kulkarni <vandita.kulkarni@intel.com>
Reviewed-by: Uma Shankar <uma.shankar@intel.com>
Signed-off-by: Uma Shankar <uma.shankar@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190730073648.5157-6-vandita.kulkarni@intel.com