drm: bridge: samsung-dsim: make samsung-dsim.h self-contained

Include <drm/drm_bridge.h> and forward declare struct platform device.

Reviewed-by: Thomas Zimmermann <[e-mail]>
Signed-off-by: Jani Nikula <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/953[e-mail]

include/drm/bridge/samsung-dsim.h

···
 #include <linux/regulator/consumer.h>
 
 #include <drm/drm_atomic_helper.h>
-#include <drm/drm_of.h>
+#include <drm/drm_bridge.h>
 #include <drm/drm_mipi_dsi.h>
+#include <drm/drm_of.h>
 
+struct platform_device;
 struct samsung_dsim;
 
 #define DSIM_STATE_ENABLED		BIT(0)