drm/mipi-dsi: Remove mipi_dsi_dcs_write_seq

There are no remaining users of mipi_dsi_dcs_write_seq and it can be
removed in favor of mipi_dsi_dcs_write_seq_multi.

Signed-off-by: Tejas Vipin <tejasvipin76@gmail.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Link: https://lore.kernel.org/r/20250419041210.515517-3-tejasvipin76@gmail.com


Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://lore.kernel.org/r/20250419041210.515517-3-tejasvipin76@gmail.com