The current implementation of platform MSI caches the msi_desc
pointer in irq_data::handler_data. This is a bit silly, as
we also have irq_data::msi_desc, which is perfectly valid.

Remove the useless assignment and simplify the whole flow.
Reported-by: NMa Jun <majun258@huawei.com>
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Reviewed-by: NJiang Liu <jiang.liu@linux.intel.com>
Link: http://lkml.kernel.org/r/1442147824-20971-1-git-send-email-marc.zyngier@arm.comSigned-off-by: NThomas Gleixner <tglx@linutronix.de>