irqchip: crossbar: Set cb pointer to null in case of error

If crossbar_of_init returns with a error, then set the cb pointer
to null.

Signed-off-by: Sricharan R <r.sricharan@ti.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Link: https://lkml.kernel.org/r/1403766634-18543-12-git-send-email-r.sricharan@ti.com


Signed-off-by: Jason Cooper <jason@lakedaemon.net>