fix: change y_col to const int8_t* for Windows Clang build compatibility

- Line 811: changed 'int8_t * y_col' to 'const int8_t * y_col'
- This fixes the const pointer mismatch error when building with Clang/ClangCL on Windows
- The variable is used with const int8_t* py, so it should also be const

Fixes issue #489

Author: Jah-yee

src/ggml-bitnet-mad.cpp

@@ -808,7 +808,7 @@ void ggml_vec_dot_i2_i8_s_Nx1(int n, float * s, size_t bs, const void * vx, size
             accu[iy] = _mm256_setzero_si256();
         }
 
-        int8_t * y_col = y + col * by;
+        const int8_t * y_col = y + col * by;
 
         for (int i = 0; i < group32_num; i++) {
             const uint8_t *px = x + i * 1024;