util: remove util_float_to_half and util_half_to_float wrappers

Acked-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6987>

src/util/format/u_format_pack.py

@@ -360,7 +360,7 @@ def conversion_expr(src_channel,
 
     # Promote half to float
     if src_type == FLOAT and src_size == 16:
-        value = 'util_half_to_float(%s)' % value
+        value = '_mesa_half_to_float(%s)' % value
         src_size = 32
 
     # Special case for float <-> ubytes for more accurate results