irqchip: crossbar: Introduce ti, max-crossbar-sources to identify valid crossbar...

irqchip: crossbar: Introduce ti, max-crossbar-sources to identify valid crossbar mapping

Currently we attempt to map any crossbar value to an IRQ, however,
this is not correct from hardware perspective. There is a max crossbar
event number upto which hardware supports. So describe the same in
device tree using 'ti,max-crossbar-sources' property and use it to
validate requests.

[ jac - remove MAX_SOURCES from binding doc, use integer because we
shouldn't put implementation details in the binding docs ]

Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Sricharan R <r.sricharan@ti.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Link: https://lkml.kernel.org/r/1403766634-18543-14-git-send-email-r.sricharan@ti.com
Signed-off-by: Jason Cooper <jason@lakedaemon.net>