arm: RTIC kernel integration to generate MP DTS

With new Boot Image header v2 the boot image header generation
decoupled from the kernel. RTIC DTS requires kernel build
environment (because of OBJDUMP, OBJCPY, and other dependencies).
The RTIC DTS will be compiled to DTB later either by
arch/arm64/boot/Makefile (for Boot Image Header v1) or by
kernel_definitions.mk (for Boot Image Header v2).

Change-Id: I299e62fa2105eb3a59df7ec9577aa2fcf193cfed
Signed-off-by: Amareswar Reddy Valasa <avalasa@codeaurora.org>