The Netx IRQs offset from zero, which is illegal, since Linux
IRQ 0 is NO_IRQ.

Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Reviewed-by: Jamie Iles <jamie@jamieiles.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>