usb: add devicetree helpers for determining dr_mode and phy_type

This adds two little devicetree helper functions for determining the
dr_mode (host, peripheral, otg) and phy_type (utmi, ulpi,...) from
the devicetree.

Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Acked-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Change-Id: Ic48843ae9e68ae4484a73d845b3187438bc337ac
Git-commit: 1c9af65357a309b60d78a442bd61d27cad458d00
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: Vijayavardhan Vennapusa <vvreddy@codeaurora.org>