[MIPS] Make I8259A_IRQ_BASE customizable

Move I8259A_IRQ_BASE from asm/i8259.h to asm/mach-generic/irq.h and
make it really customizable.  And remove I8259_IRQ_BASE declared on
some platforms.  Currently only NEC_CMBVR4133 is using custom
I8259A_IRQ_BASE value.

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/include/asm-mips/mach-generic/irq.h b/include/asm-mips/mach-generic/irq.h
index 91e6778..70d9a25 100644
--- a/include/asm-mips/mach-generic/irq.h
+++ b/include/asm-mips/mach-generic/irq.h
@@ -12,6 +12,12 @@
 #define NR_IRQS	128
 #endif
 
+#ifdef CONFIG_I8259
+#ifndef I8259A_IRQ_BASE
+#define I8259A_IRQ_BASE	0
+#endif
+#endif
+
 #ifdef CONFIG_IRQ_CPU
 
 #ifndef MIPS_CPU_IRQ_BASE