The struct ipu_platform_data is used by platform code to pass
MXC_IPU_IRQ_START to ipu-core driver.  We can save it by having
ipu-core driver call irq_alloc_descs to get the irq_base.
Signed-off-by: NShawn Guo <shawn.guo@linaro.org>
Acked-by: NVinod Koul <vinod.koul@intel.com>
Acked-by: NSascha Hauer <s.hauer@pengutronix.de>
Acked-by: NDong Aisheng <dong.aisheng@linaro.org>