Add experimental half precison support

With this MR experimental half-precision support is added

pystencils/gpu/cudajit.py

@@ -39,7 +39,10 @@ def make_python_function(kernel_function_node, argument_dict=None, custom_backen
     if argument_dict is None:
         argument_dict = {}
 
-    half = True in (field.dtype.is_half() for field in kernel_function_node.fields_accessed)
+    half = False
+    for field in kernel_function_node.fields_accessed:
+        if field.dtype.base_type is None and field.dtype.is_half:
+            half = True
 
     if cp.cuda.runtime.is_hip:
         header_list = ['"gpu_defines.h"'] + list(get_headers(kernel_function_node))