defconfig: qcs403: Add new defconfig of qcs403

QCS403 was sharing its defconfig with qcs405, separating them
out and creating its own defconfig for qcs403.

Change-Id: I7a830d407867fcb558c14c1d7b2471c269b29b1a
Signed-off-by: Avaneesh Kumar Dwivedi <akdwived@codeaurora.org>