bnxt: Don't restart on VLAN changes

In rS360398, a new iflib device method was added with default of opt out
for VLAN events needing an interface reset.

This is unintentional for bnxt(4) and is causing another bug in its VLAN
initialization code to affect the common case of adding and removing
VLANs on an existing interface.

PR: 269133
Tested by: kp
MFC after: 2 weeks
Sponsored by: BBOX.io
Differential Revision: https://reviews.freebsd.org/D41558