devlink: Add enable_sriov boolean generic parameter

enable_sriov - Enables Single-Root Input/Output Virtualization(SR-IOV)
characteristic of the device.

Reviewed-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: Vasundhara Volam <vasundhara-v.volam@broadcom.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>