Convert CONFIG_USB_KEYBOARD to Kconfig

This converts the following to Kconfig:
   CONFIG_USB_KEYBOARD

Signed-off-by: Simon Glass <sjg@chromium.org>
[trini: Fixup MPC86* configs]
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/rpi_3_defconfig b/configs/rpi_3_defconfig
index 9c08632..9b6a72f 100644
--- a/configs/rpi_3_defconfig
+++ b/configs/rpi_3_defconfig
@@ -24,6 +24,7 @@
 CONFIG_USB=y
 CONFIG_USB_STORAGE=y
 CONFIG_CONSOLE_SCROLL_LINES=10
+CONFIG_USB_KEYBOARD=y
 CONFIG_LCD=y
 CONFIG_PHYS_TO_BUS=y
 CONFIG_OF_LIBFDT=y