USB: musb: host: prevent core phy initialisation

USB: musb: host: prevent core phy initialisation

Set the new HCD flag which prevents USB core from trying to manage our
phys.

This is needed to be able to associate the controller platform device
with the glue device device-tree node on the BBB which uses legacy USB
phys. Otherwise, the generic phy lookup in usb_phy_roothub_init() and
thus HCD registration fails repeatedly with -EPROBE_DEFER (see commit
355592d55723 ("usb: core: hcd: integrate the PHY wrapper into the HCD
core")).

Note that a related phy-lookup issue was recently worked around in the
phy core by commit cb0456c3289c ("phy: work around 'phys' references to
usb-nop-xceiv devices"). Something similar may now be needed for other
USB phys, and in particular if we eventually want to let USB core manage
musb generic phys.

Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Bin Liu <b-liu@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>