tests: acpi: test short OEM_ID/OEM_TABLE_ID values in test_oem_fields()

tests: acpi: test short OEM_ID/OEM_TABLE_ID values in test_oem_fields()

Previous patch [1] added explicit whitespace padding to OEM_ID/OEM_TABLE_ID
values used in test_oem_fields() testcase to avoid false positive and
bisection issues when QEMU is switched to \0' padding. As result
testcase ceased to test values that were shorter than max possible
length values.

Update testcase to make sure that it's testing shorter IDs like it
used to before [2].

1) "tests: acpi: manually pad OEM_ID/OEM_TABLE_ID for  test_oem_fields() test"
2) 602b458201 ("acpi: Permit OEM ID and OEM table ID fields to be changed")

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Message-Id: <20220114142641.1727679-1-imammedo@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>