set up dma_ops appropriately

This patch introduces a global pointer, dma_ops, which points to an
appropriate dma_mapping_ops that the kernel should use. This is a
common way to handle multiple dma_mapping_ops (X86, POWER, and SPARC).

dma_ops is set in platform_dma_init. We also set it by hand where
machvec_init is callev via subsys_initcall.

- IA64_DIG_VTD uses vtd_dma_ops.
- IA64_HP_ZX1 uses sba_dma_ops.
- IA64_HP_ZX1_SWIOTLB uses hwsw_dma_ops.
- IA64_SGI_SN2 uses sn_dma_ops.
- The rest use swiotlb_dma_ops.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Acked-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/ia64/include/asm/machvec.h

@@ -298,6 +298,8 @@ extern void machvec_init_from_cmdline(const char *cmdline);
 #  error Unknown configuration.  Update arch/ia64/include/asm/machvec.h.
 # endif /* CONFIG_IA64_GENERIC */
 
+extern void swiotlb_dma_init(void);
+
 /*
  * Define default versions so we can extend machvec for new platforms without having
  * to update the machvec files for all existing platforms.
@@ -328,7 +330,7 @@ extern void machvec_init_from_cmdline(const char *cmdline);
 # define platform_kernel_launch_event	machvec_noop
 #endif
 #ifndef platform_dma_init
-# define platform_dma_init		swiotlb_init
+# define platform_dma_init		swiotlb_dma_init
 #endif
 #ifndef platform_dma_alloc_coherent
 # define platform_dma_alloc_coherent	swiotlb_alloc_coherent