USB: gpio-vbus: ask for vbus_draw regulator before registering xceiv

Ask for vbus_draw regulator before registering tranceiver to disallow possible
race between registration and set_power/etc.

Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Cc: Eric Miao <eric.y.miao@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>