usb: dwc3-of-simple: Add support for DRA7/AM57 platforms.

Add the compatibility with "ti,dwc3" and enable it by default if DM_USB
is enabled.

Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
diff --git a/drivers/usb/host/Kconfig b/drivers/usb/host/Kconfig
index 6ea9621..3455e81 100644
--- a/drivers/usb/host/Kconfig
+++ b/drivers/usb/host/Kconfig
@@ -24,6 +24,7 @@
 config USB_XHCI_DWC3_OF_SIMPLE
 	bool "DesignWare USB3 DRD Generic OF Simple Glue Layer"
 	depends on DM_USB
+	default y if DRA7XX
 	help
 	  Support USB2/3 functionality in simple SoC integrations with
 	  USB controller based on the DesignWare USB3 IP Core.