selftests/powerpc: Add missing files to .gitignores

These were missed when the respective tests were added, add them now.

Signed-off-by: Michael Ellerman <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

tools/testing/selftests/powerpc/math/.gitignore

···
 vmx_signal
 vsx_preempt
 fpu_denormal
+mma

tools/testing/selftests/powerpc/mce/.gitignore

···
+inject-ra-err

tools/testing/selftests/powerpc/pmu/ebb/.gitignore

···
 lost_exception_test
 no_handler_test
 cycles_with_mmcr2_test
+regs_access_pmccext_test

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

···
 rfi_flush
 entry_flush
 spectre_v2
+uaccess_flush