Import the fix from NetBSD kern/48852 (sic) to fix rockridge encoding of
device nodes

In particular, use st_rdev (the device type), not st_dev (the device inode),
and fix the comparison to be correct with the st_rdev field

Bug 203648
MFC after: 2 weeks
Submitted by: Thomas Schmitt <scdbackup@gmx.net>
Coverity CID: 1008927
Sponsored by: EMC / Isilon Storage Division