install/50808: Boot option to disable DRMKMS

[coypu%sdf.org@localhost]

>Number:         50808
>Category:       install
>Synopsis:       Boot option to disable DRMKMS
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    install-manager
>State:          open
>Class:          change-request
>Submitter-Id:   net
>Arrival-Date:   Mon Feb 15 07:30:00 +0000 2016
>Originator:     coypu
>Release:        >=7.0
>Organization:
>Environment:
NetBSD net.Home 7.99.26 NetBSD 7.99.26 (GENERIC.201602141140Z) amd64
>Description:
Perhaps very unlucky, but I encountered DRMKMS drivers problems on two machines thus far.
I believe it will friendlier to users if we had a default option to turn it off at install and boot, and at least as useful as the ability to turn off SMP.
>How-To-Repeat:

>Fix:
Maybe append a long string like: userconf disable nouveau;userconf disable radeon;userconf disable intel...