[MIPS64] Enable necessary mips64 syscalls in seccomp whitelist

Allow execution of: newfstatat, fstat and cacheflush syscalls
for mips64 arch.

Test: Boot mips64 emulator to homescreen with 3.18 kernel.
emulator -kernel prebuilts/qemu-kernel/mips64/3.18/kernel-qemu2

Change-Id: Ib5d6b0060f3e17b64d86fc944aa83a5240d512f8