firewire: core: use cleanup function in bm_work

In "bm_work" function, the references to fw_card and fw_node are
released at last. This is achieved by using goto statements. For this
case, the kernel cleanup framework is available.

This commit uses the framework to remove these statements.

Link: https://lore.kernel.org/r/20250908012108.514698-6-o-takashi@sakamocchi.jp


Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>