i40e: remove variables set but not used

The code that uses variables pe_cntx_size and pe_filt_size
has been removed, so they should be removed as well.

Eliminate the following clang warnings:
drivers/net/ethernet/intel/i40e/i40e_common.c:4139:20:
warning: variable 'pe_filt_size' set but not used.
drivers/net/ethernet/intel/i40e/i40e_common.c:4139:6:
warning: variable 'pe_cntx_size' set but not used.

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Tested-by: Gurucharan G <gurucharanx.g@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>