intel-iommu: Kill DMAR_BROKEN_GFX_WA option.

Just make it depend on BROKEN for now, in case people scream really loud
about it (and because we might want to keep some of this logic for an
upcoming BIOS workaround, so I don't just want to rip it out entirely
just yet). But for graphics devices, it really ought to be unnecessary.
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

Documentation/Intel-IOMMU.txt

@@ -56,11 +56,7 @@ Graphics Problems?
 ------------------
 If you encounter issues with graphics devices, you can try adding
 option intel_iommu=igfx_off to turn off the integrated graphics engine.
-
-If it happens to be a PCI device included in the INCLUDE_ALL Engine,
-then try enabling CONFIG_DMAR_GFX_WA to setup a 1-1 map. We hear
-graphics drivers may be in process of using DMA api's in the near
-future and at that time this option can be yanked out.
+If this fixes anything, please ensure you file a bug reporting the problem.
 
 Some exceptions to IOVA
 -----------------------

arch/x86/Kconfig

@@ -1916,7 +1916,7 @@ config DMAR_DEFAULT_ON
 config DMAR_BROKEN_GFX_WA
 	def_bool n
 	prompt "Workaround broken graphics drivers (going away soon)"
-	depends on DMAR
+	depends on DMAR && BROKEN
 	---help---
 	  Current Graphics drivers tend to use physical address
 	  for DMA and avoid using DMA APIs. Setting this config