selftests/powerpc: Add missing files to .gitignores

These were missed when the respective tests were added, add them now.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220616070705.1941829-1-mpe@ellerman.id.au

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

@@ -7,3 +7,4 @@ fpu_signal
 vmx_signal
 vsx_preempt
 fpu_denormal
+mma

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

+inject-ra-err

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

@@ -21,3 +21,4 @@ back_to_back_ebbs_test
 lost_exception_test
 no_handler_test
 cycles_with_mmcr2_test
+regs_access_pmccext_test

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

@@ -2,3 +2,4 @@
 rfi_flush
 entry_flush
 spectre_v2
+uaccess_flush