powerpc/85xx: Add SWIOTLB support to FSL boards

Add the platform-specific code for enabling SWIOTLB if needed on P2020DS,
MPC85xx DS, and MPC85xx MDS boards as they are capable of having >4G of
memory.

We determine if we need to enable swiotlb based on how much memory is in
the board and if it exceeds 4G or what we can map via PCI inbound
windows.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
diff --git a/arch/powerpc/platforms/85xx/Kconfig b/arch/powerpc/platforms/85xx/Kconfig
index 43d385c..0ee5b12c 100644
--- a/arch/powerpc/platforms/85xx/Kconfig
+++ b/arch/powerpc/platforms/85xx/Kconfig
@@ -35,12 +35,14 @@
 	select DEFAULT_UIMAGE
 	select PHYLIB
 	select HAS_RAPIDIO
+	select SWIOTLB
 	help
 	  This option enables support for the MPC85xx MDS board
 
 config MPC8536_DS
 	bool "Freescale MPC8536 DS"
 	select DEFAULT_UIMAGE
+	select SWIOTLB
 	help
 	  This option enables support for the MPC8536 DS board
 
@@ -49,6 +51,7 @@
 	select PPC_I8259
 	select DEFAULT_UIMAGE
 	select FSL_ULI1575
+	select SWIOTLB
 	help
 	  This option enables support for the MPC85xx DS (MPC8544 DS) board