ANDROID: configs: GKI: disable ARMv8.3 PAC

Moving to LLVM_IAS=1 allows for us to now emit instructions making use
of the ARMv8.3 extension Pointer Authentication (PAC), which is enabled
by default by Kconfig if the tooling supports it.

PAC has implications for DWARF based unwinders, see section 4.1.8 of
https://github.com/ARM-software/abi-aa/blob/master/aadwarf64/aadwarf64.rst#dwarf-register-names

.

Disable PAC for now until all of our DWARF based unwinders support
unwinding kernels built with PAC, particularly third party utilties that
assist with ramdump parsing.

Bug: 173653853
Bug: 174803347
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Change-Id: I4c7d9f37da7e3901de27f20bbfad4722cdb8a423