firewire: ohci: minor code refactoring for self ID logging

Current implementation to log self ID sequence has the rest to be
refactored; e.g. moving translation-unit level variables to the
dependent block.

This commit is for the purpose.

Link: https://lore.kernel.org/r/20240605235155.116468-5-o-takashi@sakamocchi.jp


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