firewire: cdev: add new event to notify request subaction with time stamp

This commit adds new event to notify event of request subaction with
time stamp field.

Current compiler implementation of System V ABI selects one of structure
members which has the maximum alignment size in the structure to decide
the size of structure. In the case of fw_cdev_event_request3 structure,
it is closure member which has 8 byte storage. The size of alignment for
the type of 8 byte storage differs depending on architectures; 4 byte for
i386 architecture and 8 byte for the others including x32 architecture.
It is inconvenient to device driver developer to use structure layout
which varies between architectures since the developer takes care of ioctl
compat layer. This commit adds 32 bit member for padding to keep the
size of structure as multiples of 8.

Cc: kunit-dev@googlegroups.com
Link: https://lore.kernel.org/r/20230529113406.986289-4-o-takashi@sakamocchi.jp


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