genirq: Introduce irq_chip.irq_compose_msi_msg() to support stacked irqchip

Add callback irq_compose_msi_msg to struct irq_chip, which will be used
to support stacked irqchip.

Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Grant Likely <grant.likely@linaro.org>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Yingjoe Chen <yingjoe.chen@mediatek.com>
Cc: Yijing Wang <wangyijing@huawei.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Hanumant Singh <hanumant@codeaurora.org>
Git-commit: 515085ef7ee74694bc9b02bc45196452defad59a
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


[pujag@codeaurora.org: resolve trivial merge conflicts]
Signed-off-by: Puja Gupta <pujag@codeaurora.org>