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/coreboot-x86_defconfig b/configs/coreboot-x86_defconfig
index 0606960..352055a 100644
--- a/configs/coreboot-x86_defconfig
+++ b/configs/coreboot-x86_defconfig
@@ -43,6 +43,7 @@
 CONFIG_USB_STORAGE=y
 CONFIG_DM_VIDEO=y
 CONFIG_VIDEO_COREBOOT=y
+CONFIG_USB_KEYBOARD=y
 CONFIG_CONSOLE_SCROLL_LINES=5
 CONFIG_USE_PRIVATE_LIBGCC=y
 CONFIG_TPM=y