usb: phy: export ulpi_viewport_access_ops

In order to build a ULPI PHY driver as a module, this symbol needs to
be exported.

Signed-off-by: Manjunath Goudar <manjunath.goudar@linaro.org>
[swarren, reworked Manjunath's patches to split them more logically]
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Felipe Balbi <balbi@ti.com>
Tested-by: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>