defconfig: msm: Disable config to append dtb image for atoll

Disable CONFIG_BUILD_ARM64_APPENDED_DTB_IMAGE for atoll,
as this is not required for boot image header v2 support.

Change-Id: I17facd04a864ca425f22978a7aa4d02f5808d5c9
Signed-off-by: Mayank Grover <groverm@codeaurora.org>