sunxi: musb: Fix some lo speed devices not working with musb host

The usb0 / otg phy on sunxi boards has a bug where it wrongly detects a
high speed squelch on usb reset deassert when a lo speed device is plugged in.

The android kernel has a work around for this in the form of temporary
disabling the phy's squelch detection on reset deassert, this commit adds
the same workaround to the u-boot sunxi musb code, thereby fixing various usb
lo speed devices not working.

Tested with a (before non working) usb keyboard and a usb 2.4 GHz wireless
keyboard/mouse combo receiver.

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