arm: soc: Add support for ARM Beetle SoC

Add SoC support for ARM Beetle platform.

Beetle is an ARM Cortex-M3 based SoC used on ARM V2M Beetle Boards.

https://www.arm.com/products/tools/development-boards/versatile-express/beetle_iot_evaluation_platform.php



This patch contains:
* The base SoC platform.
* The clock_init functionality.
* The system wide pin definitions.
* The configuarion for the drivers at SoC level (IRQs, PINs and
  Base Addr).

Jira: ZEP-1245
Change-Id: If15675935890711983e5ce37d49732b0462c3ec7
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@linaro.org>
Signed-off-by: Kumar Gala <kumar.gala@linaro.org>