Fix Sapphire Rapids never loading in Python bindings (facebookresearch#4209)

Summary:
If both `avx512` and `avx512_spr` are compiled, Sapphire Rapids capabilities are never loaded when using the Python bindings, as the `avx512` import always overrides the `avx512_spr` one.

This very small PR solves the issue.

Pull Request resolved: facebookresearch#4209

Reviewed By: mengdilin

Differential Revision: D70015045

Pulled By: gtwang01

fbshipit-source-id: d3553a6c9048a534c0901ee29e7e2354de96e79f

Author: lkuffo

faiss/python/loader.py

@@ -108,7 +108,7 @@ def is_sve_supported():
         loaded = False
 
 has_AVX512 = any("AVX512" in x.upper() for x in instruction_sets)
-if has_AVX512:
+if has_AVX512 and not loaded:
     try:
         logger.info("Loading faiss with AVX512 support.")
         from .swigfaiss_avx512 import *