build(bl1): deduplicate sources
build(bl1): deduplicate sources

Deduplicating sources prevents the build system from complaining about
multiply-compiled files, which can happen if multiple makefiles depend
on a component. This already occurs for BL31.

Signed-off-by: Chris Kay <9c0c41cd71461f9de7536bb7a214db3cff1e29f1@arm.com>
Change-Id: I9b40402f6f04600061fba7d6ad5d222a71e7d4a7

achingupta/arm-trusted-firmware,achingupta/arm-trusted-firmware