intel/fs: Make bld.F16TO32 actually emit F16TO32 not F32TO16

Ahem, "add builder helpers that work on Gfx7"...now might actually work.
Too much copy and paste...

Fixes: 966995d911 ("intel/fs: Add builder helpers for F32TO16/F16TO32 that work on Gfx7.x")
Reviewed-by: Emma Anholt <emma@anholt.net>
Reviewed-by: Faith Ekstrand <faith.ekstrand@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/21974>

src/intel/compiler/brw_fs_builder.h

@@ -685,7 +685,7 @@ namespace brw {
             return MOV(dst, src);
          } else {
             assert(shader->devinfo->ver == 7);
-            return emit(BRW_OPCODE_F32TO16,
+            return emit(BRW_OPCODE_F16TO32,
                         dst, retype(src, BRW_REGISTER_TYPE_W));
          }
       }