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/MPC8641HPCN_36BIT_defconfig b/configs/MPC8641HPCN_36BIT_defconfig
index 131a2ef..6f8d8f5 100644
--- a/configs/MPC8641HPCN_36BIT_defconfig
+++ b/configs/MPC8641HPCN_36BIT_defconfig
@@ -15,3 +15,5 @@
 CONFIG_CMD_EXT2=y
 CONFIG_SYS_NS16550=y
 CONFIG_OF_LIBFDT=y
+CONFIG_USB=y
+CONFIG_USB_KEYBOARD=y