arm64: defconfig: disable PACMan

Peripheral Access Control Manager (PACMan) is a test driver
and isn't need to be enabled by default on any target.
Also, causing OOM issues during ADSP SSR on 8937.

CRs-Fixed: 979581
Change-Id: I4a91239fb5c56c5a3e9e6a85bc1430a3060d02f1
Signed-off-by: Satya Durga Srinivasu Prabhala <satyap@codeaurora.org>