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/ge_b1x5v2_defconfig b/configs/ge_b1x5v2_defconfig
index ff14bd6..c282990 100644
--- a/configs/ge_b1x5v2_defconfig
+++ b/configs/ge_b1x5v2_defconfig
@@ -123,6 +123,7 @@
 CONFIG_SYSRESET_WATCHDOG=y
 CONFIG_IMX_THERMAL=y
 CONFIG_USB=y
+CONFIG_USB_MAX_CONTROLLER_COUNT=2
 CONFIG_USB_STORAGE=y
 CONFIG_USB_KEYBOARD=y
 CONFIG_USB_GADGET=y