IA64: Remove NULL flush_write_buffers

flush_write_buffers() in dma-mapping-common.h was removed so we
can remove NULL flush_write_buffers() in IA64.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: tony.luck@intel.com
Cc: fenghua.yu@intel.com
Cc: davem@davemloft.net
LKML-Reference: <1249872797-1314-3-git-send-email-fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/ia64/include/asm/dma-mapping.h

@@ -44,7 +44,6 @@ static inline void dma_free_coherent(struct device *dev, size_t size,
 #define dma_free_noncoherent(d, s, v, h) dma_free_coherent(d, s, v, h)
 
 #define get_dma_ops(dev) platform_dma_get_ops(dev)
-#define flush_write_buffers()
 
 #include <asm-generic/dma-mapping-common.h>