usb: xhci: Get rid of CONFIG_SYS_USB_XHCI_MAX_ROOT_PORTS

xHC reports supported maximum number of ports in the HCSPARAMS1
register, so it's unnecessary to use a hardcoded config option
CONFIG_SYS_USB_XHCI_MAX_ROOT_PORTS.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Stefan Roese <sr@denx.de>
Tested-by: Stefan Roese <sr@denx.de>
2 files changed