of/mips: Add device tree support to MIPS

Add the ability to enable CONFIG_OF on the MIPS architecture.

Signed-off-by: Dezhong Diao <dediao@cisco.com>
[grant.likely@secretlab.ca: cleared out obsolete hooks,
	removed ARCH_HAS_DEVTREE_MEM,
	remove __init tags from header file,
	removed debugfs support hunk]
[ddaney@linux-mips.org: backed out over aggressive trimming of hooks]
Acked-by: Ralf Baechle <ralf@linux-mips.org>
Tested-by: David Daney <ddaney@caviumnetworks.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
diff --git a/arch/mips/include/asm/irq.h b/arch/mips/include/asm/irq.h
index dea4aed..b003ed5 100644
--- a/arch/mips/include/asm/irq.h
+++ b/arch/mips/include/asm/irq.h
@@ -16,6 +16,11 @@
 
 #include <irq.h>
 
+static inline void irq_dispose_mapping(unsigned int virq)
+{
+	return;
+}
+
 #ifdef CONFIG_I8259
 static inline int irq_canonicalize(int irq)
 {