i40e: remove duplicate pfc stats

The pfc related priority stats are already handled separately as these
stats are actually arrays of length I40E_MAX_USER_PRIORITY. Thus,
including them within i40e_gstrings_stats will just duplicate data.

Worse, the sizeof will be incorrect, as it will be the total size of the
stat arrays, which in this case is 8 * sizeof(u64), so we will only copy
the stat contents as if they were a u32.

Since we already correctly handle these stats else where, remove them
from the i40e_gstrings_stats.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>