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/tangier/Kconfig b/arch/x86/cpu/tangier/Kconfig
index e7d16db..86a3340 100644
--- a/arch/x86/cpu/tangier/Kconfig
+++ b/arch/x86/cpu/tangier/Kconfig
@@ -13,6 +13,7 @@
 	imply MMC_SDHCI_SDMA
 	imply MMC_SDHCI_TANGIER
 	imply TANGIER_WATCHDOG
+	imply USB
 	imply USB_DWC3
 
 config SYS_CAR_ADDR