firewire: core: fix __must_hold() annotation
The variable name passed to __must_hold() annotation is invalid.
This commit fixes it.
Fixes: 420bd7068cbf ("firewire: core: use spin lock specific to transaction")
Link: https://lore.kernel.org/r/20251023104349.415310-1-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>