mac80211: only build ath10k with smallbuffers

mac80211: only build ath10k with smallbuffers

When both variants of ath10k drivers are selected, any driver that is
selected along is being built twice, one for each ath10k variant.

Avoid these redundant builds by introducing an optional second parameter
to config_package that lists the variants for which the package is to be
built.

If the symbol is to be set for all of the variants, $(ALL_VARIANTS) can
be used.  This is the case for the mac80211 and cfg80211 modules.  If
the parameter is empty, then the module will be selected and thus built
when the first variant is compiled.

Signed-off-by: Eneas U de Queiroz <cotequeiroz@gmail.com>