firewire: core: update documentation of kernel APIs for flushing completions

There is a slight difference between fw_iso_context_flush_completions() and
fw_iso_context_schedule_flush_completions().

This commit updates the documentations for them.

Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Takashi Sakamoto <[e-mail]>

drivers/firewire/core-iso.c

···
  * @ctx: the isochronous context
  *
  * Process the isochronous context in the current process context. The registered callback function
- * is called if some packets have been already transferred since the last time. If it is required
- * to process the context asynchronously, fw_iso_context_schedule_flush_completions() is available
- * instead.
+ * is called when a queued packet buffer with the interrupt flag is completed, either after
+ * transmission in the IT context or after being filled in the IR context. Additionally, the
+ * callback function is also called for the packet buffer completed at last. Furthermore, the
+ * callback function is called as well when the header buffer in the context becomes full. If it is
+ * required to process the context asynchronously, fw_iso_context_schedule_flush_completions() is
+ * available instead.
  *
  * Context: Process context. May sleep due to disable_work_sync().
  */

include/linux/firewire.h

···
  * @ctx: the isochronous context
  *
  * Schedule a work item on workqueue to process the isochronous context. The registered callback
- * function is called in the worker if some packets have been already transferred since the last
- * time. If it is required to process the context in the current context,
- * fw_iso_context_flush_completions() is available instead.
+ * function is called by the worker when a queued packet buffer with the interrupt flag is
+ * completed, either after transmission in the IT context or after being filled in the IR context.
+ * The callback function is also called when the header buffer in the context becomes full, If it
+ * is required to process the context in the current context, fw_iso_context_flush_completions() is
+ * available instead.
  *
  * Context: Any context.
  */