gallium/util: remove empty file u_half.h

Acked-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6774>

src/util/format/u_format_pack.py

@@ -715,7 +715,7 @@ def generate(formats):
     print()
     print('#include "pipe/p_compiler.h"')
     print('#include "util/u_math.h"')
-    print('#include "util/u_half.h"')
+    print('#include "util/half_float.h"')
     print('#include "u_format.h"')
     print('#include "u_format_other.h"')
     print('#include "util/format_srgb.h"')