arch: Add pmc, gpio internal Atmel SAM drivers

Added common, internal, always available SAM HAL drivers: pmc, gpio.
Note: these drivers are meant to be used by other SAM drivers, not by
a user space program directly.

Tested on Atmel SMART SAM E70 Xplained board

Origin: Original

Jira: ZEP-978
Change-Id: I00cca358f27790dc94cf79f840584b85ff5191f6
Signed-off-by: Piotr Mienkowski <Piotr.Mienkowski@schmid-telecom.ch>