driver man link absent

[systemcrash]

https://networkupstools.org/docs/man/blazer-common.html

404

[jimklimov]

Odd, where was such a link published? This is a partial document that should be included into ser and usb dirver pages.

[systemcrash]

https://networkupstools.org/docs/man/nutupsdrv.html (drivers)

[jimklimov]

Also impacts nut_usb_addvars

[jimklimov]

Oops, mis-linked from commit comments for #3253