dm: usb: Add a compatible string for PCI EHCI controller

Add a compatible string to allow this to be specified in the device tree
if needed.

Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Marek Vasut <marex@denx.de>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
1 file changed