firewire: core: code refactoring to queue work item for iso_resource

firewire: core: code refactoring to queue work item for iso_resource

The add_client_resource() function checks the type of client resource
every time to be called. If the type is for iso_resource, it schedules
work item.

However, the iso_resource client resource is only added by the call of
init_iso_resource(). There is no need to check the type every time adding
any client resource.

Link: https://lore.kernel.org/r/20260429093449.160545-3-o-takashi@sakamocchi.jp
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>