ice: introduce VF operations structure for reset flows

The ice driver currently supports virtualization using Single Root IOV,
with code in the ice_sriov.c file. In the future, we plan to also
implement support for Scalable IOV, which uses slightly different
hardware implementations for some functionality.

To eventually allow this, we introduce a new ice_vf_ops structure which
will contain the basic operations that are different between the two IOV
implementations. This primarily includes logic for how to handle the VF
reset registers, as well as what to do before and after rebuilding the
VF's VSI.

Implement these ops structures and call the ops table instead of
directly calling the SR-IOV specific function. This will allow us to
easily add the Scalable IOV implementation in the future. Additionally,
it helps separate the generalized VF logic from SR-IOV specifics. This
change allows us to move the reset logic out of ice_sriov.c and into
ice_vf_lib.c without placing any Single Root specific details into the
generic file.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Konrad Jankowski <konrad0.jankowski@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>