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/P1020RDB-PC_defconfig b/configs/P1020RDB-PC_defconfig
index 9f3a6d0..2631bb3 100644
--- a/configs/P1020RDB-PC_defconfig
+++ b/configs/P1020RDB-PC_defconfig
@@ -98,4 +98,5 @@
 CONFIG_FSL_ESPI=y
 CONFIG_USB=y
 CONFIG_USB_EHCI_FSL=y
+CONFIG_USB_MAX_CONTROLLER_COUNT=2
 CONFIG_USB_STORAGE=y