phy: add Broadcom Kona USB2 PHY driver

Add a driver for the internal Broadcom Kona USB 2.0 PHY found
on the BCM281xx family of SoCs.

Signed-off-by: Matt Porter <mporter@linaro.org>
Signed-off-by: Felipe Balbi <balbi@ti.com>

diff --cc drivers/phy/Kconfig
Simple merge

diff --cc drivers/phy/Makefile
Simple merge

diff --cc drivers/phy/phy-bcm-kona-usb2.c
Simple merge