e1000e: e1000e_enable_tx_pkt_filtering() returns wrong value

e1000e_enable_tx_pkt_filtering() will return a non-zero value if the
driver fails to enable the manageability interface on the host for
any reason; instead it should retun zero to indicate filtering has been
disabled. Also provide a single exit point for the function.

Signed-off-by: Bruce Allan <[e-mail]>
Signed-off-by: Jeff Kirsher <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/e1000e/lib.c

···
 	s32 ret_val, hdr_csum, csum;
 	u8 i, len;
 
+	hw->mac.tx_pkt_filtering = true;
+
 	/* No manageability, no filtering */
 	if (!e1000e_check_mng_mode(hw)) {
 		hw->mac.tx_pkt_filtering = false;
-		return 0;
+		goto out;
 	}
 
 	/*
···
 	 * reason, disable filtering.
 	 */
 	ret_val = e1000_mng_enable_host_if(hw);
-	if (ret_val != 0) {
+	if (ret_val) {
 		hw->mac.tx_pkt_filtering = false;
-		return ret_val;
+		goto out;
 	}
 
 	/* Read in the header.  Length and offset are in dwords. */
···
 	 */
 	if ((hdr_csum != csum) || (hdr->signature != E1000_IAMT_SIGNATURE)) {
 		hw->mac.tx_pkt_filtering = true;
-		return 1;
+		goto out;
 	}
 
 	/* Cookie area is valid, make the final check for filtering. */
 	if (!(hdr->status & E1000_MNG_DHCP_COOKIE_STATUS_PARSING)) {
 		hw->mac.tx_pkt_filtering = false;
-		return 0;
+		goto out;
 	}
 
-	hw->mac.tx_pkt_filtering = true;
-	return 1;
+out:
+	return hw->mac.tx_pkt_filtering;
 }
 
 /**