i40e: Add a FD flush counter to ethtool

This helps know how many times the interface had to flush and replay FD
filter table, which gives an indication on how often we are getting FD
table full situation.

Also check on certain pf states before proceeding to add or delete
filters since we can't add or delete filters if we are in those states.

Change-ID: I97f5bbbea7146833ea61af0e08ea794fccba1780
Signed-off-by: Anjali Singhai Jain <anjali.singhai@intel.com>
Tested-by: Jim Young <jamesx.m.young@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/i40e/i40e.h

@@ -252,6 +252,7 @@ struct i40e_pf {
 	u16 fd_sb_cnt_idx;
 	u16 fd_atr_cnt_idx;
 	unsigned long fd_flush_timestamp;
+	u32 fd_flush_cnt;
 	u32 fd_add_err;
 	u32 fd_atr_cnt;
 	u32 fd_tcp_rule;