sh: Fix OFFCHIP_IRQ_BASE compile error.

HP6xx uses OFFCHIP_IRQ_BASE to know the base irq number where non
cpu interrupts should start. This define was in irq.h before, but
since rework got lost. It really belongs inside hd64461.h since
the hp6xx wont work without it.
Signed-off-by: NKristoffer Ericson <Kristoffer.Ericson@gmail.com>
Signed-off-by: NPaul Mundt <lethal@linux-sh.org>

include/asm-sh/hd64461.h

@@ -226,6 +226,7 @@
 #define	HD64461_NIMR		(CONFIG_HD64461_IOBASE + 0x5002)
 
 #define	HD64461_IRQBASE		OFFCHIP_IRQ_BASE
+#define	OFFCHIP_IRQ_BASE	64
 #define	HD64461_IRQ_NUM		16
 
 #define	HD64461_IRQ_UART	(HD64461_IRQBASE+5)