MIPS: ath25: Remove unused DMA helper functions.

These got merged with the ath25 support after 4e7f7266 (MIPS: Remove
unnecessary platform dma helper functions) had already removed them for
all other platforms.
Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

arch/mips/include/asm/mach-ath25/dma-coherence.h

@@ -59,16 +59,6 @@ static inline int plat_dma_supported(struct device *dev, u64 mask)
 	return 1;
 }
 
-static inline void plat_extra_sync_for_device(struct device *dev)
-{
-}
-
-static inline int plat_dma_mapping_error(struct device *dev,
-					 dma_addr_t dma_addr)
-{
-	return 0;
-}
-
 static inline int plat_device_is_coherent(struct device *dev)
 {
 #ifdef CONFIG_DMA_COHERENT