net/sfc/base: support proxy auth operations for SR-IOV

net/sfc/base: support proxy auth operations for SR-IOV

VMware expects that certain kind of configurations made on the VFs are
authorized by the ESXi before these are applied e.g. assigning a MAC
address to the VF, setting MTU etc. Firmware supports a feature called
MCDI proxy which will be used to implement this authorization check.
The proxy auth module is governed by EFSYS_OPT_MCDI_PROXY_AUTH switch.
This patch adds the framework for proxy auth module along with the APIs
required for SR-IOV initialization.

Signed-off-by: Gautam Dawar <gdawar@solarflare.com>
Signed-off-by: Andrew Rybchenko <arybchenko@solarflare.com>