firewire: ohci: use devres for content of configuration ROM

The 1394 OHCI driver allocates DMA coherent buffer to transfer content
of configuration ROM.

This commit utilizes managed device resource to maintain the lifetime of
buffer.

Link: https://lore.kernel.org/r/20230604054451.161076-9-o-takashi@sakamocchi.jp


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