powerpc/QE: add support for QE USB clocks routing

This patch adds a function to the qe_lib to setup QE USB clocks routing.
To setup clocks safely, cmxgcr register needs locking, so I just reused
ucc_lock since it was used only to protect cmxgcr.

The idea behind placing clocks routing functions into the qe_lib is that
later we'll hopefully switch to the generic Linux Clock API, thus, for
example, FHCI driver may be used for QE and CPM chips without nasty #ifdefs.

This patch also fixes QE_USB_RESTART_TX command definition in the qe.h.

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Acked-By: Timur Tabi <timur@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>