[POWERPC] bootwrapper: Add fsl_get_immr() and 8xx/pq2 clock functions.

fsl_get_immr() uses /soc/ranges to determine the immr.

mpc885_get_clock() transforms a crystal frequency into a system frequency
according to the PLL register settings.

pq2_get_clocks() does the same as the above for the PowerQUICC II,
except that it produces several different clocks.

The mpc8xx/pq2 set_clocks() functions modify common properties in
the device tree based on the given clock data.

The mpc885/pq2 fixup_clocks() functions call get_clocks(), and
pass the results to set_clocks().

Signed-off-by: Scott Wood <scottwood@freescale.com>
Acked-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>