blk: Make block subsystems select BLK

The BLK symbol has a few meanings, one of which is that it controls the
driver model portion of a "block device". Rather than having this hidden
symbol be "default y if ..." it should be select'd by the various block
subsystems. Symbols such as PVBLOCK which already select'd BLK are
unchanged".

Reviewed-by: Peter Robinson <pbrobinson@gmail.com>
Reviewed-by: Quentin Schulz <quentin.schulz@cherry.de>
Signed-off-by: Tom Rini <trini@konsulko.com>

drivers/virtio/Kconfig

@@ -64,6 +64,7 @@ config VIRTIO_NET
 config VIRTIO_BLK
 	bool "virtio block driver"
 	depends on VIRTIO
+	select BLK
 	help
 	  This is the virtual block driver for virtio. It can be used with
 	  QEMU based targets.