move netdev and netlink into their own packages and out of drivers

This moves the netdev/netlink namespace out of drivers and into their
own packages.  Also, defines netdev and netlink as L3/L4 and L2 OSI
layers, respectively.  Move some L3 functionality from netlink to
netdev (GetIPAddr).

For netlink, add ConnectParams for NetConnect to pass in L2 connection
parameters (ssid, pass, auth_type, etc).  Also adds connection mode
(STA, AP, etc).

For netlink, add SendEth and RecvEthFunc funcs to handle L2 send/recv of
Ethernet pkts.

netlink/probe/wifinina.go

@@ -0,0 +1,33 @@
+//go:build pyportal || arduino_nano33 || nano_rp2040 || metro_m4_airlift || matrixportal_m4
+
+package probe
+
+import (
+	"machine"
+
+	"tinygo.org/x/drivers/netdev"
+	"tinygo.org/x/drivers/netlink"
+	"tinygo.org/x/drivers/wifinina"
+)
+
+func Probe() (netlink.Netlinker, netdev.Netdever) {
+
+	cfg := wifinina.Config{
+		// Configure SPI for 8Mhz, Mode 0, MSB First
+		Spi:  machine.NINA_SPI,
+		Freq: 8 * 1e6,
+		Sdo:  machine.NINA_SDO,
+		Sdi:  machine.NINA_SDI,
+		Sck:  machine.NINA_SCK,
+		// Device pins
+		Cs:     machine.NINA_CS,
+		Ack:    machine.NINA_ACK,
+		Gpio0:  machine.NINA_GPIO0,
+		Resetn: machine.NINA_RESETN,
+	}
+
+	nina := wifinina.New(&cfg)
+	netdev.UseNetdev(nina)
+
+	return nina, nina
+}