Fix a couple of type mismatches (facebookresearch#3059)

Summary: Pull Request resolved: facebookresearch#3059

Reviewed By: mdouze

Differential Revision: D49617392

Pulled By: mlomeli1

fbshipit-source-id: 6a81fcae7be138a734edcb3996c369256de727ba

Author: alexanderguzhva

faiss/IndexIVFFlat.cpp

@@ -46,8 +46,8 @@ IndexIVFFlat::IndexIVFFlat() {
 void IndexIVFFlat::add_core(
         idx_t n,
         const float* x,
-        const int64_t* xids,
-        const int64_t* coarse_idx) {
+        const idx_t* xids,
+        const idx_t* coarse_idx) {
     FAISS_THROW_IF_NOT(is_trained);
     FAISS_THROW_IF_NOT(coarse_idx);
     FAISS_THROW_IF_NOT(!by_residual);