kernelscripts: Avoid duplicate copy of arch include headers

Copy the ${OUT_DIR}/arch/arm64/include directory to arch/arm64
instead of arch/arm64/include to ensure that there isn't a
duplicate include directory inside of arch/arm64/include/include.

Change-Id: I8a8ba299abbf195369a2d9b858c1cb89ae518775
Signed-off-by: Isaac J. Manjarres <isaacm@codeaurora.org>