mpc83xx: add support for switching between USB Host/Function for MPC837XEMDS

With this patch u-boot can fixup the dr_mode and phy_type properties
for the Dual-Role USB controller.

While at it, also remove #ifdefs around includes, they are not needed.

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Signed-off-by: Kim Phillips <kim.phillips@freescale.com>