tests: acpi: squash sanitize_fadt_ptrs() into test_acpi_fadt_table()

tests: acpi: squash sanitize_fadt_ptrs() into test_acpi_fadt_table()

some parts of sanitize_fadt_ptrs() do redundant job
  - locating FADT
  - checking original checksum

There is no need to do it as test_acpi_fadt_table() already does that,
so drop duplicate code and move remaining fixup code into
test_acpi_fadt_table().

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Acked-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>