V4L/DVB (5587): Add help for RADIO_ADAPTERS and VIDEO_CAPTURE_DRIVERS

Add a small help for those two new Kconfig vars.

Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
diff --git a/drivers/media/radio/Kconfig b/drivers/media/radio/Kconfig
index 354d664..a6ac82a 100644
--- a/drivers/media/radio/Kconfig
+++ b/drivers/media/radio/Kconfig
@@ -6,6 +6,8 @@
 	bool "Radio Adapters"
 	depends on VIDEO_DEV
 	default y
+	---help---
+	  Say Y here to enable selecting AM/FM radio adapters.
 
 if RADIO_ADAPTERS