usb: new board-specific USB init interface

This commit unifies board-specific USB initialization implementations
under one symbol (usb_board_init), declaration of which is available in
usb.h.

New API allows selective initialization of USB controllers whenever needed.

Signed-off-by: Mateusz Zalega <m.zalega@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Reviewed-by: Lukasz Majewski <l.majewski@samsung.com>
Cc: Marek Vasut <marex@denx.de>
Cc: Lukasz Majewski <l.majewski@samsung.com>
diff --git a/drivers/usb/host/ehci-tegra.c b/drivers/usb/host/ehci-tegra.c
index c6da449..cc23133 100644
--- a/drivers/usb/host/ehci-tegra.c
+++ b/drivers/usb/host/ehci-tegra.c
@@ -699,7 +699,7 @@
 	return 0;
 }
 
-int board_usb_init(const void *blob)
+int usb_process_devicetree(const void *blob)
 {
 	int node_list[USB_PORTS_MAX];
 	int count, err = 0;