spi: apple: Add driver for Apple SPI controller

Add a driver for the SPI controller integrated on Apple SoCs.
This is necessary to support the keyboard on Apple Silicon laopts
since their keyboard uses an Apple-specific HID over SPI protocol.

Signed-off-by: Mark Kettenis <kettenis@openbsd.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
Tested on: Macbook Air M1
Tested-by: Simon Glass <sjg@chromium.org>

arch/arm/Kconfig

@@ -934,6 +934,7 @@ config ARCH_APPLE
 	select DM_MAILBOX
 	select DM_RESET
 	select DM_SERIAL
+	select DM_SPI
 	select DM_USB
 	select DM_VIDEO
 	select IOMMU
@@ -943,6 +944,7 @@ config ARCH_APPLE
 	select POSITION_INDEPENDENT
 	select POWER_DOMAIN
 	select REGMAP
+	select SPI
 	select SYSCON
 	select SYSRESET
 	select SYSRESET_WATCHDOG