x86: kconfig: Move USB to platform Kconfig

Like other peripheral drivers, move USB related drivers to platform
Kconfig as well.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/x86/cpu/qemu/Kconfig b/arch/x86/cpu/qemu/Kconfig
index ef0fd30..b6297f7 100644
--- a/arch/x86/cpu/qemu/Kconfig
+++ b/arch/x86/cpu/qemu/Kconfig
@@ -10,6 +10,8 @@
 	imply ENV_IS_NOWHERE
 	imply E1000
 	imply SYS_NS16550
+	imply USB
+	imply USB_EHCI_HCD
 	imply VIDEO_VESA
 
 if QEMU