tools: fix binding to unsupported driver

tools: fix binding to unsupported driver

The dpdk_nic_bind script will not allow ports to be bound or unbound if none of the
kernel modules supported by DPDK is loaded. This patch relaxes this restriction by
checking if a DPDK module is actually requested. The example below illustrates this
problem:

In virtio test, on the guest
1. Bind virtio port to igb_uio driver;
2. Remove igb_uio module;
3. Bind virtio port to virtio-pci driver, it fails and reports:
   "Error - no supported modules are loaded"

The script should check the to-be-bound driver flag, if it is dpdk driver(igb_uio, vfio etc),
and the corresponding module is not loaded, then exit, otherwise, just report a warning,
and continue to bind the non-dpdk driver(like virtio-pci) to dev.

Signed-off-by: Changchun Ouyang <changchun.ouyang@intel.com>
Tested-by: Qian Xu <qian.q.xu@intel.com>
Acked-by: Michael Qiu <michael.qiu@intel.com>