nanobsd: Fix cust_comconsole search patterns

[jlduran]

Summary

The current patterns are outdated, and may produce "offifexists", after
e310437971b8 ("For video consoles, only launch a getty if the device
exists.").

Fix the expressions to:

1. Disable getty(8) on the virtual syscons(4) or vt(4) terminals (/dev/ttyv*).
2. Enable the use of the first serial port as the system console.