Arm platforms: Remove common RAS configuration source

Arm platforms: Remove common RAS configuration source

The file arm_ras.c intended to provide common platform-specific RAS
configuration for Arm platforms. Because this file has symbol
definitions, it's proving difficult to provide a common definition.

This patch therefore renames and makes the file specific to FVP. Other
platforms shall provide their own configuration in similar fashion.

Change-Id: I766fd238946e3e49cdb659680e1b45f41b237901
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>