dm: cros_ec: Convert to Kconfig

Since both I2C and SPI are converted to Kconfig, we can convert cros_ec
to Kconfig for these buses.

LPC will need to wait until driver mode PCI is available.

Signed-off-by: Simon Glass <sjg@chromium.org>

drivers/input/Kconfig

@@ -0,0 +1,6 @@
+config CROS_EC_KEYB
+	bool "Enable Chrome OS EC keyboard support"
+	help
+	  Most ARM Chromebooks use an EC to provide access to the keyboard.
+	  Messages are used to request key scans from the EC and these are
+	  then decoded into keys by this driver.