ARM: ux500: split out prcmu initialization

This untangles the final bits of the prcmu code from the platform
code:

* The IRQ_PRCMU_* definitions move from irqs-db8500.h into prcmu.c
  because they are only of local significance.
* u8500_thsens_device goes into the prcmu, because it uses a PRCMU
  IRQ that the platform does not see.
* IRQ_DB8500_AB8500 and IRQ_PRCMU_BASE go into the platform data
  because the PRCMU does not see it.

Acked-by: Samuel Ortiz <sameo@linux.intel.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
[Fixed a oneliner bug]
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>