staging: fwserial: delete the driver.

In the years since it was added (2012), no one has stepped up to
maintain this properly and get it merged into the kernel tree.  So
remove it as it's obviously not being used.

If it is being used, we can easily revert this and take the time to get
it out of the staging tree.

Link: https://lore.kernel.org/r/20220924105817.808385-1-gregkh@linuxfoundation.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>