ice: Get resources per function

ice_get_guar_num_vsi currently calculates the number of VSIs per PF.
Rework this into a general function ice_get_num_per_func, that can
calculate per PF allocations for not just VSIs but across multiple
resource types.

Signed-off-by: Brett Creeley <brett.creeley@intel.com>
Reviewed-by: Bruce Allan <bruce.w.allan@intel.com>
Signed-off-by: Anirudh Venkataramanan <anirudh.venkataramanan@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>