plat/arm/board/sgi: Add board support for SGI-575 platform

SGI-575 consists of two clusters of four Cortex-A75 CPU's each.
The FVP for this platform does not support system suspend and
resume functionality as there is no wakeup source supported.
So all the system suspend and resume related tests are skipped.

Change-Id: I758069d5ad1a3e3868260960b879a5a4d6b26496
Signed-off-by: Chandni Cherukuri <chandni.cherukuri@arm.com>