usb: phy: twl6030-usb: fix possible use-after-free on remove

In remove(), use cancel_delayed_work_sync() to cancel the
delayed work. Otherwise there's a chance that this work
will continue to run until after the device has been removed.

This issue was detected with the help of Coccinelle.

Cc: Tony Lindgren <tony@atomide.com>
Cc: Bin Liu <b-liu@ti.com>
Fixes: b6a619a8 ("usb: phy: Check initial state for twl6030")
Signed-off-by: Sven Van Asbroeck <TheSven73@gmail.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>