Fix sys.fs.tmpfs.mknod_test.{char, block} by reverting r321967

In r321967 ngie "fixed" these tests by changing their expectations to match
the device numbers produced by the new ino64 code. But it wasn't the tests
that were broken, it was the kernel. bde fixed the kernel in r335053.

Reported by: Jenkins
MFC after: Never (only applies to >= 12)