i.MX31: Clock Control Module

i.MX31: Clock Control Module

For Linux to be able to work out how fast its clocks are going, so
that timer ticks come approximately at the right time, it needs to
be able to query the clock control module (CCM).

This is the start of a CCM implementation.  It currently knows only about
the MCU, HSP and IPG clocks --- i.e., the ones used to feed the periodic
and general purpose timers.

Signed-off-by: Peter Chubb <peter.chubb@nicta.com.au>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>