ipoctal: request_irq after configuration

The request for an IRQ handler must be done after whole configuration. This
was not the case for this driver which request the IRQ in the middle of
the configuration. Sometimes, it happens that something is not completely
configured, we recieve an interrupt thus we stumble into troubles in the
IRQ handler.

Signed-off-by: Federico Vaga <federico.vaga@cern.ch>
Acked-by: Samuel Iglesias Gonsalvez <siglesias@igalia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>