ARM: dts: pxa: add clocks

Add clocks to the IPs already described in the pxa device-tree
files. There are more clocks in the clock tree than IPs described in the
current pxa device-tree.

This patch ensures that :
 - the current description is correct
 - the clocks are actually claimed, so that clock framework doesn't
   disable them automatically (unused clocks shutdown)

Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>