staging: unisys: Process more than one response per check

When s-Par is in polling mode it checks every 2 ms to see if there is
a response from the IO service partition in the queue. Currently it
just reads one entry per 2 ms, this needs to be changed so it drains
the queue on each check.

Signed-off-by: David Kershner <david.kershner@unisys.com>
Signed-off-by: Benjamin Romer <benjamin.romer@unisys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>