ice: rename ICE_MAX_VF_COUNT to avoid confusion

The ICE_MAX_VF_COUNT field is defined in ice_sriov.h. This count is true
for SR-IOV but will not be true for all VF implementations, such as when
the ice driver supports Scalable IOV.

Rename this definition to clearly indicate ICE_MAX_SRIOV_VFS.

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>