staging: wilc1000: removes unused local variable

This patch removes unused local variable.
This variable is operation definition that back off from sending packets
for some time.
However, that has been deleted operation code.
That is removes all relative code.

Signed-off-by: Leo Kim <leo.kim@atmel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>