Add support to simultaneous AP and mesh roles with wl18xx

Currently, with kernel 4.19, it's not possible to set wl18xx devices in AP + Mesh mode.
To accomplish that the following patch must be applied:
```diff
diff --git a/drivers/net/wireless/ti/wl18xx/main.c b/drivers/net/wireless/ti/wl18xx/main.c
index 496b9b63cea1..db5bc51ce51c 100644
--- a/drivers/net/wireless/ti/wl18xx/main.c
+++ b/drivers/net/wireless/ti/wl18xx/main.c
@@ -1905,12 +1905,14 @@ wl18xx_iface_combinations[] = {
.max_interfaces = 3,
.limits = wl18xx_iface_limits,
.n_limits = ARRAY_SIZE(wl18xx_iface_limits),
+ .beacon_int_min_gcd = 1,
.num_different_channels = 2,
},
{
.max_interfaces = 2,
.limits = wl18xx_iface_ap_limits,
.n_limits = ARRAY_SIZE(wl18xx_iface_ap_limits),
+ .beacon_int_min_gcd = 1,
.num_different_channels = 1,
.radar_detect_widths = BIT(NL80211_CHAN_NO_HT) |
BIT(NL80211_CHAN_HT20) |
```
See the following post in TI's Wi-Fi Forum for extra details:

[WL1835MOD: Unable to activate simultaneous AP and mesh roles](https://e2e.ti.com/support/wireless-connectivity/wifi/f/968/t/900338)