drm/bridge: samsung-dsim: allow configuring the VIDEO_MODE bit

drm/bridge: samsung-dsim: allow configuring the VIDEO_MODE bit

The VIDEO_MODE bit of DSIM_CONFIG is hardcoded to BIT(25), but
Exynos7870's DSIM has it in BIT(18) as per downstream kernel sources.

In order to support both, move this bit value to the driver data struct
and define it for every driver compatible. Reference the value from
there instead, in functions wherever required.

Signed-off-by: Kaustabh Chakraborty <kauschluss@disroot.org>
Signed-off-by: Inki Dae <inki.dae@samsung.com>