nios2: dma-mapping.h: change ioremap to map_physmem

Change ioremap() to map_physmem(), as it is more used in u-boot.

Signed-off-by: Thomas Chou <thomas@wytron.com.tw>
Reviewed-by: Marek Vasut <marex@denx.de>

arch/nios2/include/asm/dma-mapping.h

@@ -19,6 +19,6 @@ static inline void *dma_alloc_coherent(size_t len, unsigned long *handle)
 	if (handle)
 		*handle = addr;
 
-	return ioremap(addr, len);
+	return map_physmem(addr, len, MAP_NOCACHE);
 }
 #endif /* __ASM_NIOS2_DMA_MAPPING_H */