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This patch:
- Add the __COHERENT_RAM_START__ and __COHERENT_RAM_END__ symbols.
- Improve how the symbols are found with a regex.
- Add a build option to revert the memory layout output.

Change-Id: I54ec660261431bc98d78acb0f80e3d95bc5397ac
Signed-off-by: Louis Mayencourt <louis.mayencourt@arm.com>