Only enable BLOCK_COMPAT if COMPAT is needed

IOW, it needs to depend on both CONFIG_BLOCK and CONFIG_COMPAT.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

block/Kconfig

@@ -62,10 +62,11 @@ config BLK_DEV_BSG
 	protocols (e.g. Task Management Functions and SMP in Serial
 	Attached SCSI).
 
+endif # BLOCK
+
 config BLOCK_COMPAT
 	bool
+	depends on BLOCK && COMPAT
 	default y
 
-endif # BLOCK
-
 source block/Kconfig.iosched