vhost: drop vringh dependency

vringh isn't used by vhost net or scsi - it's used
by CAIF only at the moment. Drop the dependency.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/vhost/Kconfig

@@ -2,7 +2,6 @@ config VHOST_NET
 	tristate "Host kernel accelerator for virtio net"
 	depends on NET && EVENTFD && (TUN || !TUN) && (MACVTAP || !MACVTAP)
 	select VHOST
-	select VHOST_RING
 	---help---
 	  This kernel module can be loaded in host kernel to accelerate
 	  guest networking with virtio_net. Not to be confused with virtio_net
@@ -15,7 +14,6 @@ config VHOST_SCSI
 	tristate "VHOST_SCSI TCM fabric driver"
 	depends on TARGET_CORE && EVENTFD && m
 	select VHOST
-	select VHOST_RING
 	default n
 	---help---
 	Say M here to enable the vhost_scsi TCM fabric module