media: si470x: add missing MODULE_DESCRIPTION() macro

With ARCH=x86, make allmodconfig && make W=1 C=1 reports:
WARNING: modpost: missing MODULE_DESCRIPTION() in drivers/media/radio/si470x/radio-si470x-common.o

Add the missing invocation of the MODULE_DESCRIPTION() macro.
Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>

drivers/media/radio/si470x/radio-si470x-common.c

@@ -790,4 +790,5 @@ const struct video_device si470x_viddev_template = {
 };
 EXPORT_SYMBOL_GPL(si470x_viddev_template);
 
+MODULE_DESCRIPTION("Core radio driver for Si470x FM Radio Receivers");
 MODULE_LICENSE("GPL");