defconfig: msm: Disable CONFIG_BUILD_ARM64_APPENDED_DTB_IMAGE flag

To support Boot image with header version V2, disable
CONFIG_BUILD_ARM64_APPENDED_DTB flag in defconfig and
perf_defconfig for sdm660.

Change-Id: I758761c1328ea42d0951b570b99cdeba2e37c4eb
Signed-off-by: Rahul Shahare <rshaha@codeaurora.org>