devmatch: introduce quiet command line option

In setups without hints whatsoever one can get a long list of
"Can't read linker hints file" error messages during boot.
Add a -q/--quiet option which would suppress the noise and leave
space for more essential information.

While here switch to a pre-defined exit code from sysexits.

MFC after: 4 weeks
Reviewed by: imp
Differential Revision: https://reviews.freebsd.org/D41443