qeth: avoid loop if ipa command response is missing

If qeth issues an ipa command, but for some reasons the response
never comes back, qeth reaches a timeout.
Reset the irq_pending flag of the write channel in timeout handling
code and trigger a recovery to avoid endless looping for the following
ipa command.

Signed-off-by: Ursula Braun <ursula.braun@de.ibm.com>
Signed-off-by: Frank Blaschka <frank.blaschka@de.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>