arm64: Disable ARMv8.1, ARMv8.2 architectural features

Some of the ARMv8.1, ARMv8.2 architectural features(ARM64_HW_AFDBM,
ARM64_PAN and ARM64_UAO) are enabled by default. Do not enable
these features by default, so that target specific defconfig
files can enable or disable based on features supported.

Change-Id: I072216927c3475169156a3d51f20d06675630ab9
Signed-off-by: Prasad Sodagudi <psodagud@codeaurora.org>