broadcom-wl: fix compilation with 4.14

The last_rx field was removed from net_device. Since the field wasn't
used by the generic subsystem, and the driver only writes to it, just
remove the usage.

Signed-off-by: Jonas Gorski <jonas.gorski@gmail.com>

package/kernel/broadcom-wl/patches/040-remove_last_rx_usage.patch

@@ -0,0 +1,10 @@
+--- broadcom-wl-5.10.56.27.3/driver/wl_linux.c.orig	2018-01-13 18:25:14.944667645 +0100
++++ broadcom-wl-5.10.56.27.3/driver/wl_linux.c	2018-01-13 18:25:25.836667888 +0100
+@@ -2762,7 +2762,6 @@
+ 	bcopy(oskb->data + D11_PHY_HDR_LEN, pdata, oskb->len - D11_PHY_HDR_LEN);
+ 
+ 	skb->dev = wl->monitor;
+-	skb->dev->last_rx = jiffies;
+ #if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 22)
+ 	skb_reset_mac_header(skb);
+ #else