configure: Fix non-public symbol regex
configure: Fix non-public symbol regex

We want to only detect function declarations, so we only
want to match spaces in between the type and the lsmash_-prefixed
function name, and 0 or 1 asterisks.

Signed-off-by: Derek Buitenhuis <aff7d637ede26ea82e5226e01b697996cc52e526@gmail.com>

silverfilain/L-SMASH,silverfilain/L-SMASH,silverfilain/L-SMASH,l-smash/l-smash,l-smash/l-smash,l-smash/l-smash