irqchip: crossbar: Fix sparse and checkpatch warnings

There is absolutely no need for crossbar driver to expose functions and
variables into global namespace. So make them all static

Also fix a couple of checkpatch warnings.

Fixes sparse warnings:
drivers/irqchip/irq-crossbar.c:129:29: warning: symbol 'routable_irq_domain_ops' was not declared. Should it be static?
drivers/irqchip/irq-crossbar.c:261:12: warning: symbol 'irqcrossbar_init' was not declared. Should it be static?

Checkpatch warnings:
WARNING: Prefer kcalloc over kzalloc with multiply
+	cb->irq_map = kzalloc(max * sizeof(int), GFP_KERNEL);

WARNING: Prefer kcalloc over kzalloc with multiply
+	cb->register_offsets = kzalloc(max * sizeof(int), GFP_KERNEL);

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/1403766634-18543-8-git-send-email-r.sricharan@ti.com


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