irq_data_get_irq_chip() can return NULL, however it is expected that this
never happens. If a buggy driver leads to NULL being returned from
irq_data_get_irq_chip(), warn about it instead of crashing the machine.
Signed-off-by: Marek Vasut <marex@denx.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

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