Define driver interface

This interface must be implemented by all device drivers in the driver
sub-packages.

src/gopheros/device/driver.go

@@ -0,0 +1,15 @@
+package device
+
+import "gopheros/kernel"
+
+// Driver is an interface implemented by all drivers.
+type Driver interface {
+	// DriverName returns the name of the driver.
+	DriverName() string
+
+	// DriverVersion returns the driver version.
+	DriverVersion() (major uint16, minor uint16, patch uint16)
+
+	// DriverInit initializes the device driver.
+	DriverInit() *kernel.Error
+}