bsg: Kconfig updates

This updates bsg entry in Kconfig:

- bsg supports sg v4
- bsg depends on SCSI
- it might be better to mark it experimental for a while

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

block/Kconfig

@@ -53,9 +53,10 @@ endif # BLOCK
 
 config BLK_DEV_BSG
 	bool "Block layer SG support"
+	depends on SCSI && EXPERIMENTAL
 	default y
 	---help---
-	Saying Y here will enable generic SG (SCSI generic) v3
+	Saying Y here will enable generic SG (SCSI generic) v4
 	support for any block device.
 
 source block/Kconfig.iosched