staging: unisys: remove unused struct members

The following struct members were never used:
 putfile_active_buffer::pnext
 putfile_request::file_request_number
 putfile_request::data_sequence_number

Signed-off-by: Erik Arfvidson <erik.arfvidson@unisys.com>
Signed-off-by: David Kershner <david.kershner@unisys.com>
Reviewed-by: Luis de Bethencourt <luisbg@osg.samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>