clocks: advance towards a more pure DT setup

Essentially, instead of calling mx51_clocks_init_dt() we now call
imx5_clocks_init (which is in drivers/clk/clk-imx.c). And MX53
does the same meaning in actual fact the timer_init functions
could be merged together.

(except for the fact that this is probably the best and only place
to do the iim_en/read_rev/iim_dis bit which is still fairly
SoC-dependent, I would have done that already).

rename the clock functions from mxfoo to imxfoo to maybe do
something about differentiating us between non-DT kernels which
would still want to call mxc_do_this or mx5_hack_from_years_ago
or whatever.

Add ccm device tree ids to the clk-imx driver, so that when we call
imx5_clocks_init it also initializes the ccm driver. Remove the
explicit call to imx5_clocks_init from the ccm driver.

Add a workaround to clk-imx.c such that PLL and fixed rate clocks
will always be registered before CCM does since it doesn't matter
what order you register the clocks in, as long as they are all
registered before you intend to USE one of them;

* unfortunately in this case the CCM module uses a bunch of them
  to reset parents and set rates as little specific hacks
* at least pll3, pll2 and osc are needed needed before the CCM module
  has fully finished
* and since we're called from .timer_init we cannot hang around or
  do a probe deferral.

There shouldn't be any need to be sure that the fixed and pll clocks
are seperately registered at this stage.