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 <tzimmermann@suse.de>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/9534ca7dfba96580950e116c84ce0fa68fdf93a4.1709749576.git.jani.nikula@intel.com

include/drm/bridge/samsung-dsim.h

@@ -11,9 +11,11 @@
 #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)