m32r: remove unused flush_write_buffers definition

Signed-off-by: Christoph Hellwig <hch@lst.de>

arch/m32r/include/asm/io.h

@@ -191,8 +191,6 @@ static inline void _writel(unsigned long l, unsigned long addr)
 
 #define mmiowb()
 
-#define flush_write_buffers() do { } while (0)  /* M32R_FIXME */
-
 static inline void
 memset_io(volatile void __iomem *addr, unsigned char val, int count)
 {