imx: move gpio init after to irq init

The commit 9a763bf "get rid of mxc_gpio_init" changed gpio_init
and irq_init sequence. Usually we will call set_irq_chained_handler
in gpio_init functions, this should be called after the irq_init
called, otherwise the chained irq can't get propoer irq_chip and this
irq will remain masked even we called set_irq_chained_handler.

Signed-off-by: Jason Wang <jason77.wang@gmail.com>
Tested-by: Eric Bénard <eric@eukrea.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>