www/chromium: Un-remove v4l video capture support

This support was removed in r416521. The revision message did not document the
removal nor justify patching out a major port feature.

This restores that support.

The earlier revision should probably be audited for other patches which (a) add
update burden to this already huge port and (b) remove expected functionality.

PR: 245250
Submitted by: Tamas Szakaly <sghctoma AT gmail.com>
Reported by: yuri@
Approved by: jrm
Differential Revision: https://reviews.freebsd.org/D24330