usb: dra7xx: Add support for dra7xx xhci USB host

Add the support for the dra7xx xhci usb host.
dra7xx does not contain an EHCI controller so the headers
can be removed from the board file.

The xHCI host on dra7xx is connected to a usb2 phy so need to
add support to enable those clocks.

Signed-off-by: Dan Murphy <dmurphy@ti.com>
diff --git a/drivers/usb/host/xhci-omap.c b/drivers/usb/host/xhci-omap.c
index 7292ed8..f6099ac 100644
--- a/drivers/usb/host/xhci-omap.c
+++ b/drivers/usb/host/xhci-omap.c
@@ -98,9 +98,7 @@
 {
 	int ret = 0;
 
-	omap_enable_phy_clocks(omap);
-
-	omap_usb3_phy_init(omap->usb3_phy);
+	omap_enable_phy(omap);
 
 	ret = dwc3_core_init(omap->dwc3_reg);
 	if (ret) {
@@ -116,7 +114,7 @@
 
 static void omap_xhci_core_exit(struct omap_xhci *omap)
 {
-	usb3_phy_power(0);
+	usb_phy_power(0);
 }
 
 int xhci_hcd_init(int index, struct xhci_hccr **hccr, struct xhci_hcor **hcor)