x86: Add dma-mapping.h to architectural code

Some cross-platform drivers rely on this header present.
Make it so for x86.

It's just a copy'n'paste of arch/arm/include/asm/dma-mapping.h.

Suggested-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

arch/x86/include/asm/dma-mapping.h

@@ -0,0 +1,41 @@
+/*
+ * (C) Copyright 2007
+ * Stelian Pop <stelian@popies.net>
+ * Lead Tech Design <www.leadtechdesign.com>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+#ifndef __ASM_X86_DMA_MAPPING_H
+#define __ASM_X86_DMA_MAPPING_H
+
+#define	dma_mapping_error(x, y)	0
+
+enum dma_data_direction {
+	DMA_BIDIRECTIONAL	= 0,
+	DMA_TO_DEVICE		= 1,
+	DMA_FROM_DEVICE		= 2,
+};
+
+static inline void *dma_alloc_coherent(size_t len, unsigned long *handle)
+{
+	*handle = (unsigned long)memalign(ARCH_DMA_MINALIGN, len);
+	return (void *)*handle;
+}
+
+static inline void dma_free_coherent(void *addr)
+{
+	free(addr);
+}
+
+static inline unsigned long dma_map_single(volatile void *vaddr, size_t len,
+					   enum dma_data_direction dir)
+{
+	return (unsigned long)vaddr;
+}
+
+static inline void dma_unmap_single(volatile void *vaddr, size_t len,
+				    unsigned long paddr)
+{
+}
+
+#endif /* __ASM_X86_DMA_MAPPING_H */