ice: convert ice_for_each_vf to include VF entry iterator

The ice_for_each_vf macro is intended to be used to loop over all VFs.
The current implementation relies on an iterator that is the index into
the VF array in the PF structure. This forces all users to perform a
look up themselves.

This abstraction forces a lot of duplicate work on callers and leaks the
interface implementation to the caller. Replace this with an
implementation that includes the VF pointer the primary iterator. This
version simplifies callers which just want to iterate over every VF, as
they no longer need to perform their own lookup.

The "i" iterator value is replaced with a new unsigned int "bkt"
parameter, as this will match the necessary interface for replacing
the VF array with a hash table. For now, the bkt is the VF ID, but in
the future it will simply be the hash bucket index. Document that it
should not be treated as a VF ID.

This change aims to simplify switching from the array to a hash table. I
considered alternative implementations such as an xarray but decided
that the hash table was the simplest and most suitable implementation. I
also looked at methods to hide the bkt iterator entirely, but I couldn't
come up with a feasible solution that worked for hash table iterators.

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>