staging: unisys: visornic - correctly reset flag prior to send_enbdis()

Because devdata->enab_dis_acked is the flag used to determine whether an
enable/disable operation to the IO partition has completed, it should
always be cleared prior to initiating the operation.  The call added to
visornic_enable_with_timeout() added in this patch makes the usage there
consistent with visornic_disable_with_timeout().

Signed-off-by: Tim Sell <Timothy.Sell@unisys.com>
Signed-off-by: Benjamin Romer <benjamin.romer@unisys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>