sunxi: musb: Add id pin support

When in host mode check if there is a host cable inserted into the otg
port by checking the id pin. If there is no host cable return an error to
make usb_lowlevel_init() exit early, rather then waiting for 1 second
for a device which will never show up.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Ian Campbell <ijc@hellion.org.uk>