i2c: switch all i2c drivers definitions to use i2c bus interface type instead of machine package concrete type

Signed-off-by: deadprogram <ron@hybridgroup.com>

blinkm/blinkm.go

@@ -1,15 +1,14 @@
 // Package blinkm implements a driver for the BlinkM I2C RGB LED.
 //
 // Datasheet: http://thingm.com/fileadmin/thingm/downloads/BlinkM_datasheet.pdf
+//
 package blinkm // import "tinygo.org/x/drivers/blinkm"
 
-import (
-	"machine"
-)
+import "tinygo.org/x/drivers"
 
 // Device wraps an I2C connection to a BlinkM device.
 type Device struct {
-	bus     machine.I2C
+	bus     drivers.I2C
 	Address uint16
 }
 
@@ -17,7 +16,7 @@ type Device struct {
 // configured.
 //
 // This function only creates the Device object, it does not touch the device.
-func New(bus machine.I2C) Device {
+func New(bus drivers.I2C) Device {
 	return Device{bus, Address}
 }