[BLOCK] Only include the compat ioctl code if CONFIG_BLOCK is set

Add an extra CONFIG_BLOCK_COMPAT that we can use in the Makefile
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

block/Kconfig

@@ -62,6 +62,10 @@ config BLK_DEV_BSG
 	protocols (e.g. Task Management Functions and SMP in Serial
 	Attached SCSI).
 
+config BLOCK_COMPAT
+	bool
+	default y
+
 endif # BLOCK
 
 source block/Kconfig.iosched

block/Makefile

@@ -11,4 +11,4 @@ obj-$(CONFIG_IOSCHED_DEADLINE)	+= deadline-iosched.o
 obj-$(CONFIG_IOSCHED_CFQ)	+= cfq-iosched.o
 
 obj-$(CONFIG_BLK_DEV_IO_TRACE)	+= blktrace.o
-obj-$(CONFIG_COMPAT)		+= compat_ioctl.o
+obj-$(CONFIG_BLOCK_COMPAT)	+= compat_ioctl.o