libloc: Drop loc_database_add_as symbol definition

libloc: Drop loc_database_add_as symbol definition

This database_add_as function was superseded by writer_add_as back
in c182393, however the `libloc.sym` file was never updated. This
commit cleans up the exported functions list.

On GNU's ld, this stray function definition gets ignored, but other
linkers could refuse to link (such as LLD 16+), as they would assume
a misconfiguration has taken place.

Signed-off-by: Valters Jansons <valter.jansons@gmail.com>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>