uml: fix compile error in dma_get_cache_alignment()

Fix uml compile error:

  include/linux/dma-mapping.h:145: error: redefinition of 'dma_get_cache_alignment'
  arch/um/include/asm/dma-mapping.h:99: note: previous definition of 'dma_get_cache_alignment' was here

Introduced by commit 4565f017 ("dma-mapping: unify
dma_get_cache_alignment implementations")
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: Jeff Dike <jdike@addtoit.com>
Cc: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

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

@@ -95,13 +95,6 @@ dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg, int nelems,
 #define dma_alloc_noncoherent(d, s, h, f) dma_alloc_coherent(d, s, h, f)
 #define dma_free_noncoherent(d, s, v, h) dma_free_coherent(d, s, v, h)
 
-static inline int
-dma_get_cache_alignment(void)
-{
-	BUG();
-	return(0);
-}
-
 static inline void
 dma_cache_sync(struct device *dev, void *vaddr, size_t size,
 	       enum dma_data_direction direction)