Add missing #include in code_distance-sve.h (#4219)

Summary:
Pull Request resolved: #4219

`code_distance-sve.h` references `PQDecoder8` but doesn't include the header. The issue is revealed by D68784260 which removed some includes from a header that indirectly included `ProductQuantizer.h`

```
headers/faiss/impl/code_distance/code_distance-sve.h:74:45: error: unknown type name 'PQDecoder8'; did you mean 'PQDecoderT'?
       74 | std::enable_if_t<std::is_same_v<PQDecoderT, PQDecoder8>, float> inline distance_single_code_sve(
          |                                             ^~~~~~~~~~
          |                                             PQDecoderT
```

Reviewed By: ddrcoder

Differential Revision: D70433576

fbshipit-source-id: 12945b16003a3d6a995b18ffe9798179ecf826f4

Author: sqi-mt

faiss/impl/code_distance/code_distance-sve.h

@@ -14,6 +14,7 @@
 #include <tuple>
 #include <type_traits>
 
+#include <faiss/impl/ProductQuantizer.h>
 #include <faiss/impl/code_distance/code_distance-generic.h>
 
 namespace faiss {
@@ -48,7 +49,7 @@ static inline void distance_codes_kernel(
     partialSum = svadd_f32_m(pg, partialSum, collected);
 }
 
-static float distance_single_code_sve_for_small_m(
+static inline float distance_single_code_sve_for_small_m(
         // the product quantizer
         const size_t M,
         // precomputed distances, layout (M, ksub)