ACPI ERST: bios-tables-test.c steps 1 and 2

ACPI ERST: bios-tables-test.c steps 1 and 2

Following the guidelines in tests/qtest/bios-tables-test.c, this
change adds empty placeholder files per step 1 for the new ERST
table, and excludes resulting changed files in bios-tables-test-allowed-diff.h
per step 2.

Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>
Acked-by: Igor Mammedov <imammedo@redhat.com>
Message-Id: <1643402289-22216-2-git-send-email-eric.devolder@oracle.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>