staging: et131x: Fix add_timer() from et131x_open

The error_timer was only getting initialised and an initial jiffies value set following a probe.
This could result in the timer needlessly expiring immediately after et131x_open is called.
Now this is all done from the open call instead.

Signed-off-by: Mark Einon <mark.einon@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>