fs: touch up predicts in putname()

1. we already expect the refcount is 1.
2. path creation predicts name == iname

I verified this straightens out the asm, no functional changes.

Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
Link: https://patch.msgid.link/20251029134952.658450-1-mjguzik@gmail.com
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>