vdpa: move to drivers/vdpa

We have both vhost and virtio drivers that depend on vdpa.
It's easier to locate it at a top level directory otherwise
we run into issues e.g. if vhost is built-in but virtio
is modular. Let's just move it up a level.

Reported-by: Randy Dunlap <[e-mail]>
Signed-off-by: Michael S. Tsirkin <[e-mail]>

MAINTAINERS

···
 S:	Maintained
 F:	Documentation/devicetree/bindings/virtio/
 F:	drivers/virtio/
+F:	drivers/vdpa/
 F:	tools/virtio/
 F:	drivers/net/virtio_net.c
 F:	drivers/block/virtio_blk.c

drivers/Kconfig

···
 
 source "drivers/virtio/Kconfig"
 
+source "drivers/vdpa/Kconfig"
+
 source "drivers/vhost/Kconfig"
 
 source "drivers/hv/Kconfig"

drivers/Makefile

···
 obj-y				+= soc/
 
 obj-$(CONFIG_VIRTIO)		+= virtio/
+obj-$(CONFIG_VDPA)		+= vdpa/
 obj-$(CONFIG_XEN)		+= xen/
 
 # regulators early, since some subsystems rely on them to initialize

drivers/virtio/Kconfig

···
 	 If unsure, say 'N'.
 
 endif # VIRTIO_MENU
-
-source "drivers/virtio/vdpa/Kconfig"

drivers/virtio/Makefile

···
 obj-$(CONFIG_VIRTIO_BALLOON) += virtio_balloon.o
 obj-$(CONFIG_VIRTIO_INPUT) += virtio_input.o
 obj-$(CONFIG_VIRTIO_VDPA) += virtio_vdpa.o
-obj-$(CONFIG_VDPA) += vdpa/