usb: chipidea: imx: make MODULE_LICENCE and SPDX-identifier match

The SPDX-License-Identifier is set to GPL-2.0+, which correspond to
MODULE_LICENSE "GPL".

Signed-off-by: Marcus Folkesson <marcus.folkesson@gmail.com>
Signed-off-by: Peter Chen <peter.chen@nxp.com>