isl_basic_map_drop: drop error label
isl_basic_map_drop: drop error label

This is a minor code clean-up that make it easier to extract
isl_basic_map_drop_core in the next commit.

Signed-off-by: Sven Verdoolaege <235c10dd23b819f81cdc9756a251746bc184cab6@gmail.com>

Meinersbur/isl,Meinersbur/isl,Meinersbur/isl,Meinersbur/isl