dma: fix build error after update to v3.19

Signed-off-by: Steven Miao <realmz6@gmail.com>

arch/blackfin/include/asm/io.h

diff --git a/arch/blackfin/include/asm/io.h b/arch/blackfin/include/asm/io.h
index b03ac90..4e8ad05 100644
--- a/arch/blackfin/include/asm/io.h
+++ b/arch/blackfin/include/asm/io.h
@@ -35,14 +35,6 @@
 #define insw insw
 #define insl insl
 
-extern void dma_outsb(unsigned long port, const void *addr, unsigned short count);
-extern void dma_outsw(unsigned long port, const void *addr, unsigned short count);
-extern void dma_outsl(unsigned long port, const void *addr, unsigned short count);
-
-extern void dma_insb(unsigned long port, void *addr, unsigned short count);
-extern void dma_insw(unsigned long port, void *addr, unsigned short count);
-extern void dma_insl(unsigned long port, void *addr, unsigned short count);
-
 /**
  * I/O write barrier
  *