freebsd_network: Always hold the "Giant" lock during attaches.

Reduces patches to OpenBSD drivers slightly, and could potentially
help with some of the KDLs.

src/add-ons/kernel/drivers/network/wlan/iaxwifi200/dev/pci/if_iwx.c

@@ -11028,9 +11028,7 @@ iwx_attach(struct device *parent, struct device *self, void *aux)
 	ic->ic_ampdu_tx_stop = NULL;
 
 #ifdef __HAIKU__
-	mtx_lock(&Giant);
 	iwx_preinit(sc);
-	mtx_unlock(&Giant);
 #else
 	/*
 	 * We cannot read the MAC address without loading the

src/add-ons/kernel/drivers/network/wlan/idualwifi7260/dev/pci/if_iwm.c

@@ -12124,9 +12124,7 @@ iwm_attach(struct device *parent, struct device *self, void *aux)
 	ic->ic_ampdu_tx_start = iwm_ampdu_tx_start;
 	ic->ic_ampdu_tx_stop = iwm_ampdu_tx_stop;
 #ifdef __HAIKU__
-	mtx_lock(&Giant);
 	iwm_preinit(sc);
-	mtx_unlock(&Giant);
 #else
 	/*
 	 * We cannot read the MAC address without loading the

src/libs/compat/freebsd_network/device.c

@@ -481,6 +481,9 @@ device_attach(device_t device)
 		|| device->methods.attach == NULL)
 		return B_ERROR;
 
+	// Always hold the giant lock during attach.
+	mtx_lock(&Giant);
+
 	result = device->methods.attach(device);
 
 	if (result == 0)
@@ -489,6 +492,7 @@ device_attach(device_t device)
 	if (result == 0 && HAIKU_DRIVER_REQUIRES(FBSD_WLAN_FEATURE))
 		result = start_wlan(device);
 
+	mtx_unlock(&Giant);
 	return result;
 }