nds32: remove __virt_to_bus and __bus_to_virt

These macros are not used anywhere.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Greentime Hu <greentime@andestech.com>
Signed-off-by: Greentime Hu <greentime@andestech.com>

arch/nds32/include/asm/memory.h

@@ -15,14 +15,6 @@
 #define PHYS_OFFSET     (0x0)
 #endif
 
-#ifndef __virt_to_bus
-#define __virt_to_bus	__virt_to_phys
-#endif
-
-#ifndef __bus_to_virt
-#define __bus_to_virt	__phys_to_virt
-#endif
-
 /*
  * TASK_SIZE - the maximum size of a user space task.
  * TASK_UNMAPPED_BASE - the lower boundary of the mmap VM area