usb: ulpi: Define a *otg_ulpi_create no-op

Building a kernel for imx_v4_v5_defconfig with CONFIG_USB_ULPI disabled, results
in the following error:

arch/arm/mach-imx/built-in.o: In function 'pca100_init':
platform-mx2-emma.c:(.init.text+0x6788): undefined reference to 'otg_ulpi_create'
platform-mx2-emma.c:(.init.text+0x682c): undefined reference to 'mxc_ulpi_access_ops'

Fix this by providing a no-op definition of *otg_ulpi_create for the case when
CONFIG_USB_ULPI is not defined.

Acked-by: Igor Grinberg <grinberg@compulab.co.il>
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>