smartd.cpp: Add '-q *nodev0*' option variants.

These change the exit status to 0 if there are no devices
to monitor.
smartd.8.in: Document new functionality.

git-svn-id: https://svn.code.sf.net/p/smartmontools/code/trunk@5323 4ea69e1a-61f1-4043-bf83-b5c94c648137