vdpa: remove unnecessary 'default n' in Kconfig entries

'default n' is not necessary since it is already the default when
nothing is specified.
Suggested-by: Jason Wang <jasowang@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Link: https://lore.kernel.org/r/20201215144256.155342-2-sgarzare@redhat.comSigned-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/vdpa/Kconfig

@@ -14,7 +14,6 @@ config VDPA_SIM
 	select DMA_OPS
 	select VHOST_RING
 	select GENERIC_NET_UTILS
-	default n
 	help
 	  vDPA networking device simulator which loop TX traffic back
 	  to RX. This device is used for testing, prototyping and
@@ -23,7 +22,6 @@ config VDPA_SIM
 config IFCVF
 	tristate "Intel IFC VF vDPA driver"
 	depends on PCI_MSI
-	default n
 	help
 	  This kernel module can drive Intel IFC VF NIC to offload
 	  virtio dataplane traffic to hardware.
@@ -42,7 +40,6 @@ config MLX5_VDPA_NET
 	tristate "vDPA driver for ConnectX devices"
 	select MLX5_VDPA
 	depends on MLX5_CORE
-	default n
 	help
 	  VDPA network driver for ConnectX6 and newer. Provides offloading
 	  of virtio net datapath such that descriptors put on the ring will