Fix the fp8 gemm for large tensors on MI300. (#1011)

* Fix the fp8 conversion

* Try clipping value before conversion

* Fix return

* Simplify with a const

* reduce the gemm input tensor values to reduce round-off error

* replace if-else with lambda

* fix syntax

---------

Co-authored-by: Rostyslav Geyyer <rosty.geyyer@amd.com>

[ROCm/composable_kernel commit: f46a6ffad8]

include/ck/utility/type_convert.hpp

@@ -100,6 +100,8 @@ template <>
 inline __host__ __device__ f8_t type_convert<f8_t, float>(float x)
 {
 #if defined(__gfx940__) || defined(__gfx941__) || defined(__gfx942__)
+    float max_fp8 = 240.0f;
+    x             = x > max_fp8 ? max_fp8 : (x < -max_fp8 ? -max_fp8 : x);
     union
     {
         float fval;