net/bnxt: add port representor infrastructure

Defines data structures and code to init/uninit
VF representors during pci_probe and pci_remove
respectively.
Most of the dev_ops for the VF representor are just
stubs for now and will be will be filled out in next patch.

To create a representor using testpmd:
testpmd -c 0xff -wB:D.F,representor=1 -- -i
testpmd -c 0xff -w05:02.0,representor=[1] -- -i

To create a representor using ovs-dpdk:
1. First add the trusted VF port to a bridge
ovs-vsctl add-port ovsbr0 vf_rep1 -- set Interface vf_rep1 type=dpdk
options:dpdk-devargs=0000:06:02.0
2. Add the representor port to the bridge
ovs-vsctl add-port ovsbr0 vf_rep1 -- set Interface vf_rep1 type=dpdk
options:dpdk-devargs=0000:06:02.0,representor=1

Signed-off-by: Somnath Kotur <somnath.kotur@broadcom.com>
Signed-off-by: Venkat Duvvuru <venkatkumar.duvvuru@broadcom.com>
Reviewed-by: Kalesh AP <kalesh-anakkur.purayil@broadcom.com>
Reviewed-by: Ajit Khaparde <ajit.khaparde@broadcom.com>