firewire: core: replace local macros with common inline functions for isochronous packet header

This commit replaces the local macros with the common inline functions
to serialize the packer header for Asynchronous Streaming Packet.

Link: https://lore.kernel.org/r/20240428071347.409202-9-o-takashi@sakamocchi.jp


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