[MIPS] Remove duplicate ISA DMA code for 0 DMA channel case.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/include/asm-mips/dma.h b/include/asm-mips/dma.h
index e85849a..23f789c 100644
--- a/include/asm-mips/dma.h
+++ b/include/asm-mips/dma.h
@@ -74,7 +74,9 @@
  *
  */
 
+#ifndef GENERIC_ISA_DMA_SUPPORT_BROKEN
 #define MAX_DMA_CHANNELS	8
+#endif
 
 /*
  * The maximum address in KSEG0 that we can perform a DMA transfer to on this