usb: chipidea: usbmisc_imx6q: Staticize usbmisc_imx6q_drv_init/exit()

Staticize usbmisc_imx6q_drv_init/exit() to fix the following sparse warnings:

drivers/usb/chipidea/usbmisc_imx6q.c:147:12: warning: symbol 'usbmisc_imx6q_drv_init' was not declared. Should it be static?
drivers/usb/chipidea/usbmisc_imx6q.c:153:13: warning: symbol 'usbmisc_imx6q_drv_exit' was not declared. Should it be static?

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>