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/mx6ul_14x14_evk_defconfig b/configs/mx6ul_14x14_evk_defconfig
index 10f6b4f..784a5d9 100644
--- a/configs/mx6ul_14x14_evk_defconfig
+++ b/configs/mx6ul_14x14_evk_defconfig
@@ -93,6 +93,7 @@
 CONFIG_SOFT_SPI=y
 CONFIG_IMX_THERMAL=y
 CONFIG_USB=y
+CONFIG_USB_MAX_CONTROLLER_COUNT=2
 CONFIG_USB_STORAGE=y
 CONFIG_USB_GADGET=y
 CONFIG_USB_GADGET_MANUFACTURER="FSL"