rename initializer to NewSPI per Go convention

see: tinygo-org#196 (review)

Author: ardnew

examples/ili9341/pyportal_boing/feather-stm32f405.go

@@ -11,17 +11,17 @@ import (
 var (
 	csPin   = machine.D12
 	dcPin   = machine.D10
-	display = ili9341.NewSpi(
+	display = ili9341.NewSPI(
 		machine.SPI0,
 		dcPin,
 		csPin,
-		machine.D8, // if wired to 3.3, pick an unused pin
+		machine.D8, // if wired to 3.3V, pick an unused pin
 	)
 
 	// ILI9341's LED pin. set this to an unused pin (but not NoPin!) if
 	// wired via resistor straight to 3.3V. the boing example tries to
 	// set this pin and will panic if NoPin is used.
-	backlight = machine.D9
+	backlight = machine.D13
 )
 
 func init() {

ili9341/spi_stm32f4.go

@@ -11,7 +11,7 @@ type spiDriver struct {
 	bus machine.SPI
 }
 
-func NewSpi(bus machine.SPI, dc, cs, rst machine.Pin) *Device {
+func NewSPI(bus machine.SPI, dc, cs, rst machine.Pin) *Device {
 	return &Device{
 		dc:  dc,
 		cs:  cs,