drm/tidss: Check for K2G in in dispc_softreset()

drm/tidss: Check for K2G in in dispc_softreset()

K2G doesn't have softreset feature. Instead of having every caller of
dispc_softreset() check for K2G, move the check into dispc_softreset(),
and make dispc_softreset() return 0 in case of K2G.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Aradhya Bhatia <a-bhatia1@ti.com>
Link: https://lore.kernel.org/r/20231109-tidss-probe-v2-6-ac91b5ea35c0@ideasonboard.com
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>