mpc83xx: USB: Reorganized its support

The following patch reorganizes/reworks the USB support for mpc83xx
as under:-

  * Moves the 83xx USB clock init from drivers/usb/host/ehci-fsl.c to
    cpu/mpx83xx/cpu_init.c

  * Board specific usb_phy_type is read from the environment

  * Adds USB EHCI specific structure in include/usb/ehci-fsl.h

  * Copyrights revamped in most of the following files

Signed-off-by: Vivek Mahajan <vivek.mahajan@freescale.com>
Signed-off-by: Remy Bohmer <linux@bohmer.net>