usb: move CONFIG_USB_XHCI_DWC3 to Kconfig

Create an entry for "config USB_XHCI_DWC3" in Kconfig and
switch over to it for all boards.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/configs/peach-pi_defconfig b/configs/peach-pi_defconfig
index 9a815d0..3c403ba 100644
--- a/configs/peach-pi_defconfig
+++ b/configs/peach-pi_defconfig
@@ -56,6 +56,7 @@
 CONFIG_USB=y
 CONFIG_DM_USB=y
 CONFIG_USB_XHCI_HCD=y
+CONFIG_USB_XHCI_DWC3=y
 CONFIG_VIDEO_BRIDGE=y
 CONFIG_VIDEO_BRIDGE_PARADE_PS862X=y
 CONFIG_TPM=y