ice: convert vf->vc_ops to a const pointer

ice: convert vf->vc_ops to a const pointer

The vc_ops structure is used to allow different handlers for virtchnl
commands when the driver is in representor mode. The current
implementation uses a copy of the ops table in each VF, and modifies
this copy dynamically.

The usual practice in kernel code is to store the ops table in a
constant structure and point to different versions. This has a number of
advantages:

  1. Reduced memory usage. Each VF merely points to the correct table,
     so they're able to re-use the same constant lookup table in memory.
  2. Consistency. It becomes more difficult to accidentally update or
     edit only one op call. Instead, the code switches to the correct
     able by a single pointer write. In general this is atomic, either
     the pointer is updated or its not.
  3. Code Layout. The VF structure can store a pointer to the table
     without needing to have the full structure definition defined prior
     to the VF structure definition. This will aid in future refactoring
     of code by allowing the VF pointer to be kept in ice_vf_lib.h while
     the virtchnl ops table can be maintained in ice_virtchnl.h

There is one major downside in the case of the vc_ops structure. Most of
the operations in the table are the same between the two current
implementations. This can appear to lead to duplication since each
implementation must now fill in the complete table. It could make
spotting the differences in the representor mode more challenging.
Unfortunately, methods to make this less error prone either add
complexity overhead (macros using CPP token concatenation) or don't work
on all compilers we support (constant initializer from another constant
structure).

The cost of maintaining two structures does not out weigh the benefits
of the constant table model.

While we're making these changes, go ahead and rename the structure and
implementations with "virtchnl" instead of "vc_vf_". This will more
closely align with the planned file renaming, and avoid similar names when
we later introduce a "vf ops" table for separating Scalable IOV and
Single Root IOV implementations.

Leave the accessor/assignment functions in order to avoid issues with
compiling with options disabled. The interface makes it easier to handle
when CONFIG_PCI_IOV is disabled in the kernel.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Sandeep Penigalapati <sandeep.penigalapati@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>