#1585 nvcc throws a lot of warnings during build

描述

It's probably worth fixing.

Some of them:

```
/llm/Strata/src/kernels/cuda/iq_kernels.cu(3229): warning #128-D: loop is not reachable
              for (int j = 0; j < cn; ++j) {
              ^
          detected during instantiation of "void strata::kernels::native_gu_lds_kernel<TG,SG,TI>(const unsigned long long *, const int32_t *, const int32_t *, const int32_t *, const block_q8_1 *, strata::kernels::NativeExpertLayout, float *, float *) [with TG=23, SG=1, TI=true]" at line 3528

/llm/Strata/src/kernels/cuda/iq_kernels.cu(3229): warning #128-D: loop is not reachable
              for (int j = 0; j < cn; ++j) {
              ^
          detected during instantiation of "void strata::kernels::native_gu_lds_kernel<TG,SG,TI>(const unsigned long long *, const int32_t *, const int32_t *, const int32_t *, const block_q8_1 *, strata::kernels::NativeExpertLayout, float *, float *) [with TG=22, SG=1, TI=true]" at line 3529

/llm/Strata/src/kernels/cuda/iq_kernels.cu(2844): warning #20058-D: the #pragma unroll must precede a loop
  #pragma unroll
          ^
          detected during instantiation of "void strata::kernels::native_gu_amd_kernel<TG,MODE>(const unsigned long long *, const int32_t *, const int32_t *, const int32_t *, const block_q8_1 *, strata::kernels::NativeExpertLayout, float *, float *) [with TG=16, MODE=1]" at line 3543

/llm/Strata/src/kernels/cuda/iq_kernels.cu(596): warning #177-D: function "strata::kernels::<unnamed>::Fmt<14>::dot" was declared but never referenced
                static float dot(const void* v, const block_q8_1* y, int kbx, int iqs) { return vec_dot_q6_K_q8_1(v, y, kbx, iqs); } };
                             ^

/llm/Strata/src/kernels/cuda/iq_kernels.cu(595): warning #177-D: member "strata::kernels::<unnamed>::Fmt<14>::qk" was declared but never referenced
  template<> struct Fmt<14> { static constexpr int qk = 256, ipb = (256 / (4*2)) / VDR_Q6_K, step = VDR_Q6_K;
                                                   ^

/llm/Strata/src/kernels/cuda/iq_kernels.cu(595): warning #177-D: member "strata::kernels::<unnamed>::Fmt<14>::ipb" was declared but never referenced
  template<> struct Fmt<14> { static constexpr int qk = 256, ipb = (256 / (4*2)) / VDR_Q6_K, step = VDR_Q6_K;
                                                             ^

/llm/Strata/src/kernels/cuda/iq_kernels.cu(595): warning #177-D: member "strata::kernels::<unnamed>::Fmt<14>::step" was declared but never referenced
  template<> struct Fmt<14> { static constexpr int qk = 256, ipb = (256 / (4*2)) / VDR_Q6_K, step = VDR_Q6_K;
```