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/imx6dl_mamoj_defconfig b/configs/imx6dl_mamoj_defconfig
index 8669217..067498d 100644
--- a/configs/imx6dl_mamoj_defconfig
+++ b/configs/imx6dl_mamoj_defconfig
@@ -63,6 +63,7 @@
 CONFIG_IMX_THERMAL=y
 CONFIG_USB=y
 # CONFIG_SPL_DM_USB is not set
+CONFIG_USB_MAX_CONTROLLER_COUNT=2
 CONFIG_USB_GADGET=y
 CONFIG_USB_GADGET_MANUFACTURER="FSL"
 CONFIG_USB_GADGET_VENDOR_NUM=0x0525