tools: ynl-gen: move local vars after the opening bracket

The "function writing helper" tries to put local variables
between prototype and the opening bracket. Clearly wrong,
but up until now nothing actually uses it to write local
vars so it wasn't noticed.

Reviewed-by: Donald Hunter <donald.hunter@gmail.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Link: https://patch.msgid.link/20250414211851.602096-3-kuba@kernel.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>