USB: ci13xxx_msm: add module license

Since commit "193ab2a6 usb: gadget: allow multiple gadgets to be built"
the udc controllers can be compiled as a module. The ci13xxx_msm driver
is missing the MODULE_LICENSE statement, so loading fails with:

ci13xxx_msm: module license 'unspecified' taints kernel.
ci13xxx_msm: Unknown symbol dev_set_name (err 0)
ci13xxx_msm: Unknown symbol platform_get_irq (err 0)
ci13xxx_msm: Unknown symbol device_unregister (err 0)
ci13xxx_msm: Unknown symbol usb_add_gadget_udc (err 0)
ci13xxx_msm: Unknown symbol put_device (err 0)
ci13xxx_msm: Unknown symbol platform_driver_register (err 0)
ci13xxx_msm: Unknown symbol platform_get_resource (err 0)
ci13xxx_msm: Unknown symbol device_register (err 0)
ci13xxx_msm: Unknown symbol usb_del_gadget_udc (err 0)

This patch adds the missing MODULE_LICENSE statement with GPL v2 according
to the header of the driver.

Tested-by: Pavankumar Kondeti <pkondeti@codeaurora.org>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>