[PATCH 5/5] selftests/pstore: add testcases for multiple pmsg instances

To test multiple pmsg, we should check that /dev/pmsg[N] (N > 0) is available. After reboot, we should check that pmsg-[backend]-[N] which keeps content is detected even if pmsg-[backend]-[N-M] (0 < M <= N) doesn't exist due to lack of contents. So we add the following testcases. - pstore_tests

[PATCH 5/5] selftests/pstore: add testcases for multiple pmsg instances

To test multiple pmsg, we should check that /dev/pmsg[N] (N > 0) is available. After reboot, we should check that pmsg-[backend]-[N] which keeps content is detected even if pmsg-[backend]-[N-M] (0 < M <= N) doesn't exist due to lack of contents. So we add the following testcases. - pstore_tests