sh: dma: Make PVR2 DMA configurable.

With arch/sh/drivers/dma/ always being built, the Dreamcast DMA engines
are being unconditionally built in, regardless of whether the DMA API is
enabled or not. This is a regression from previous behaviour, but there
is not much advantage in building them all in unconditionally regardless.
Add a new config option to make it optional, and update the only user of
it to reflect that.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>
diff --git a/arch/sh/drivers/dma/Kconfig b/arch/sh/drivers/dma/Kconfig
index 32bb8fa..ae26610 100644
--- a/arch/sh/drivers/dma/Kconfig
+++ b/arch/sh/drivers/dma/Kconfig
@@ -54,4 +54,17 @@
 	  of the SH7760.
 	  Say Y if you want to use Audio/USB DMA on your SH7760 board.
 
+config PVR2_DMA
+	tristate "PowerVR 2 DMAC support"
+	depends on SH_DREAMCAST && SH_DMA
+	help
+	  Selecting this will enable support for the PVR2 DMA controller.
+	  As this chains off of the on-chip DMAC, that must also be
+	  enabled by default.
+
+	  This is primarily used by the pvr2fb framebuffer driver for
+	  certain optimizations, but is not necessary for functionality.
+
+	  If in doubt, say N.
+
 endmenu