ARM: bcm281xx: Add timer driver (driver portion)

ARM: bcm281xx: Add timer driver (driver portion)

This adds support for the Broadcom timer, used in the following SoCs:
BCM11130, BCM11140, BCM11351, BCM28145, BCM28155

Updates from V6:
- Split DT portion into a separate patch

Updates from V5:
- Rebase to latest arm-soc/for-next

Updates from V4:
- Switch code to use CLOCKSOURCE_OF_DECLARE

Updates from V3:
- Migrate to 3.9 timer framework updates

Updates from V2:
- prepend static fns + fields with kona_

Updates from V1:
- Rename bcm_timer.c to bcm_kona_timer.c
- Pull .h into bcm_kona_timer.c
- Make timers static
- Clean up comment block
- Switched to using clockevents_config_and_register
- Added an error to the get_timer loop if it repeats too much
- Added to Documentation/devicetree/bindings/arm/bcm/bcm,kona-timer.txt
- Added missing readl to timer_disable_and_clear

Note: bcm,kona-timer was kept as the 'compatible' field to make it
specific enough for when there are multiple bcm timers (bcm,timer is
too generic).

Signed-off-by: Christian Daudt <csd@broadcom.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: John Stultz <john.stultz@linaro.org>
Reviewed-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>