drm/bridge: synopsys: dw-mipi-dsi: Add mode fixup support

Vendor drivers may need to fixup mode due to pixel clock tree limitation,
so introduce the ->mode_fixup() callcack to struct dw_mipi_dsi_plat_data
and call it at atomic check stage if available.

Signed-off-by: Liu Ying <victor.liu@nxp.com>
Reviewed-by: Robert Foss <rfoss@kernel.org>
Signed-off-by: Robert Foss <rfoss@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230821034008.3876938-5-victor.liu@nxp.com