usb: typec: fusb302: Make fusb302_irq_work static

Fix sparse warning:

drivers/usb/typec/tcpm/fusb302.c:1454:6: warning:
 symbol 'fusb302_irq_work' was not declared. Should it be static?

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Reviewed-by: Mukesh Ojha <mojha@codeaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>