staging: fsl-mc: make function its_fsl_mc_msi_init static

The function its_fsl_mc_msi_init is local to the source and does
not need to be in global scope, so make it static.

Cleans up sparse warning:
symbol 'its_fsl_mc_msi_init' was not declared. Should it be static?
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/fsl-mc/bus/irq-gic-v3-its-fsl-mc-msi.c

@@ -67,7 +67,7 @@ static const struct of_device_id its_device_id[] = {
 	{},
 };
 
-int __init its_fsl_mc_msi_init(void)
+static int __init its_fsl_mc_msi_init(void)
 {
 	struct device_node *np;
 	struct irq_domain *parent;