usb: chipidea: ci_hdrc_imx: access phy via private data

commit ea1418b5f1a (usb: chipidea: i.MX: use devm_usb_get_phy_by_phandle to get
phy) causes the USB host to miss the disconnect/connect events.

In order to reproduce this problem:

- Insert a USB thumb into the USB host port (connection is detected)
- Remove it (no disconnect event will be reported)
- Insert the USB thumb again (connection is not detected)

Fix this problem by accessing the usb_phy structure using the private data
instead of accessing a local structure.

Tested on a mx28evk board.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Acked-by: Peter Chen <peter.chen@freescale.com>
Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>