perf arch powerpc: Sync powerpc syscall.tbl with the kernel sources

To get the changes in:

  fbcee2eb ("powerpc/32: Always save non volatile GPRs at syscall entry")

That shouldn't cause any change in tooling, just silences the following
tools/perf/ build warning:

  Warning: Kernel ABI header at 'tools/perf/arch/powerpc/entry/syscalls/syscall.tbl' differs from latest version at 'arch/powerpc/kernel/syscalls/syscall.tbl'

Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>