usb: chipidea: don't clobber return value of ci_role_start()

If a role fails to start, propagate the error code up the call stack
from probe.

Signed-off-by: Lothar Waßmann <LW@KARO-electronics.de>
Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>