firewire: ohci: minor code refactoring to localize text table

firewire: ohci: minor code refactoring to localize text table

The string table for tcode is just used by log_ar_at_event(). In the case,
it is suitable to move the table inner the function definition.

This commit is for the purpose. Additionally, the hard-coded value for
tcode is replaced with defined macros as many as possible.

Link: https://lore.kernel.org/r/20240729134631.127189-3-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>