usb: phy: move msm_hsusb.h into driver

As a preparation for another cleanup, this moves the header file
for the phy-msm-usb driver into the driver itself. No other file
includes it any more, and we don't really want it in the global
namespace anyway.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>