While only the first PHY supports mode switching, the remaining PHYs
work in USB host mode. They should support set_mode with mode=USB_HOST
instead of failing. This is especially needed now that the USB core does
set_mode for all USB ports, which was added in commit b97a3134 ("usb:
core: comply to PHY framework").

Make set_mode with mode=USB_HOST a no-op instead of failing for the
non-OTG USB PHYs.

Fixes: 6ba43c29 ("phy-sun4i-usb: Add support for phy_set_mode")
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>