Convert CONFIG_USB_MAX_CONTROLLER_COUNT to Kconfig

This converts the following to Kconfig:
   CONFIG_USB_MAX_CONTROLLER_COUNT

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/lx2160aqds_tfa_defconfig b/configs/lx2160aqds_tfa_defconfig
index e8ae5af..b6441a3 100644
--- a/configs/lx2160aqds_tfa_defconfig
+++ b/configs/lx2160aqds_tfa_defconfig
@@ -112,6 +112,7 @@
 CONFIG_USB=y
 CONFIG_USB_XHCI_HCD=y
 CONFIG_USB_XHCI_DWC3=y
+CONFIG_USB_MAX_CONTROLLER_COUNT=2
 CONFIG_WDT=y
 CONFIG_WDT_SBSA=y
 CONFIG_EFI_LOADER_BOUNCE_BUFFER=y