ice: remove unused definitions from ice_sriov.h

A few more macros exist in ice_sriov.h which are not used anywhere.
These can be safely removed. Note that ICE_VIRTCHNL_VF_CAP_L2 capability
is set but never checked anywhere in the driver. Thus it is also safe to
remove.

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>