arm64: Add config support to build qcs405 platforms

Add "ARCH_QCS405" config option to compile kernel for QCS405 SoC.

Change-Id: Id899e95d8ff6c32f8e787e5e9cd701228c9ae0b6
Signed-off-by: Avaneesh Kumar Dwivedi <akdwived@codeaurora.org>