metal : try to fix BF16 support check

ggml-ci

Author: ggerganov

ggml/src/ggml-metal.m

@@ -496,10 +496,6 @@ @implementation GGMLMetalClass
                 // dictionary of preprocessor macros
                 NSMutableDictionary * prep = [NSMutableDictionary dictionary];
 
-                if (!ctx_dev->has_bfloat) {
-                    [prep setObject:@"GGML_METAL_NO_BFLOAT" forKey:@"GGML_METAL_NO_BFLOAT"];
-                }
-
                 MTLCompileOptions * options = [MTLCompileOptions new];
                 options.preprocessorMacros = prep;
 

ggml/src/ggml-metal.metal

@@ -12,6 +12,10 @@ using namespace metal;
 
 #define N_SIMDWIDTH 32 // assuming SIMD group size is 32
 
+#if !defined(__BFLT16_M_PI__)
+#define GGML_METAL_NO_BFLOAT
+#endif
+
 #if !defined(GGML_METAL_NO_BFLOAT)
 typedef matrix<bfloat, 4, 4> bfloat4x4;
 #endif