greybus: gpio: fix generic_handle_irq_desc api change

The generic_handle_irq_desc api only have changed in 4.3.0, so check
against the correct version, if not will break builds for 4.2.x.

Fixes: e7895cfc476 ("gpio: handle api change in generic_handle_irq_desc()")
Signed-off-by: Rui Miguel Silva <rui.silva@linaro.org>
Reviewed-by: Johan Hovold <johan@hovoldconsulting.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>