drm: Add MIPI read_multi func and two write macros

drm: Add MIPI read_multi func and two write macros

Create mipi_dsi_dcs_read_multi(), which accepts a mipi_dsi_multi_context
struct for improved error handling and cleaner panel driver code.

Create mipi_dsi_dcs_write_var_seq_multi() and
mipi_dsi_generic_write_var_seq_multi() macros which allow MIPI panel
drivers to write non-constant data to display controllers.

Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Brigham Campbell <me@brighamcampbell.com>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20250731032343.1258366-3-me@brighamcampbell.com