i2c: Don't print uninitialized data when verbose

i2c -sv or i2c -rv prints an uninitialized field i2c_opt.addr.
Suppress the verbose message entirely for scan and reset,
where it provides no information, and zero initialize the field.

See https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=279261

Reviewed by: imp
Pull Request: https://github.com/freebsd/freebsd-src/pull/1345