selftests/powerpc: update .gitignore

I did an in-place build of the self-tests and found that it left
the tree dirty.

Add missed test binaries to .gitignore
Signed-off-by: NDaniel Axtens <dja@axtens.net>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201201144427.1228745-1-dja@axtens.net

tools/testing/selftests/powerpc/nx-gzip/.gitignore

+# SPDX-License-Identifier: GPL-2.0-only
+gunz_test
+gzfht_test

tools/testing/selftests/powerpc/security/.gitignore

 # SPDX-License-Identifier: GPL-2.0-only
 rfi_flush
 entry_flush
+spectre_v2

tools/testing/selftests/powerpc/signal/.gitignore

@@ -3,3 +3,4 @@ signal
 signal_tm
 sigfuz
 sigreturn_vdso
+sig_sc_double_restart

tools/testing/selftests/powerpc/syscalls/.gitignore

 # SPDX-License-Identifier: GPL-2.0-only
 ipc_unmuxed
+rtas_filter