staging: octeon-hcd: Directly include linux/of.h

This drivers currently obtains linux/of.h by luck and a chain of
bizarre inclusions, which we're about to fix.

Let's include the required file directly.
Signed-off-by: Marc Zyngier <maz@kernel.org>

drivers/staging/octeon-usb/octeon-hcd.c

@@ -50,8 +50,10 @@
 #include <linux/module.h>
 #include <linux/usb/hcd.h>
 #include <linux/prefetch.h>
+#include <linux/irqdomain.h>
 #include <linux/dma-mapping.h>
 #include <linux/platform_device.h>
+#include <linux/of.h>
 
 #include <asm/octeon/octeon.h>