[media] smiapp: Allow using external clock from the clock framework

Instead of providing a function in platform data, allow also providing the
name of the external clock and use it through the clock framework.

Signed-off-by: Sakari Ailus <sakari.ailus@maxwell.research.nokia.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

include/media/smiapp.h

@@ -77,6 +77,7 @@ struct smiapp_platform_data {
 	struct smiapp_flash_strobe_parms *strobe_setup;
 
 	int (*set_xclk)(struct v4l2_subdev *sd, int hz);
+	char *ext_clk_name;
 	int xshutdown;			/* gpio or SMIAPP_NO_XSHUTDOWN */
 };