fix: refine backend error message to include ROCM_HOME

Signed-off-by: fishingfly <zhoyuzf@163.com>

setup.py

@@ -316,7 +316,7 @@ class CMakeBuild(BuildExtension):
         elif ROCM_HOME is not None:
             cmake_args += ["-DKTRANSFORMERS_USE_ROCM=ON"]
         else:
-            raise ValueError("Unsupported backend: CUDA_HOME and MUSA_HOME are not set.")
+            raise ValueError("Unsupported backend: CUDA_HOME, MUSA_HOME, and ROCM_HOME are not set.")
         # log cmake_args
         print("CMake args:", cmake_args)