netsnmp: install all MIB files

netsnmp: install all MIB files

Since commit be8e32d585f3 ("netsnmp: configurable MIB modules"),
the list of MIB modules can be selected with a configuration option.

However, there was still an hardcoded list of MIB files to exclude from
the target filesystem.
Since it is complicated to know which MIB files are necessary according
to the configuration, let's install all of them.

Cc: przemyslaw <przemyslaw.wrzos@calyptech.com>
Cc: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Julien Floret <julien.floret@6wind.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>