sh: Make dma-isa depend on ISA_DMA_API.

Previously we linked in the ISA DMA wrapper unconditionally.
As there are very few users of this, it's better to make it
conditional.
Signed-off-by: NPaul Mundt <lethal@linux-sh.org>

arch/sh/drivers/dma/Makefile

@@ -2,8 +2,8 @@
 # Makefile for the SuperH DMA specific kernel interface routines under Linux.
 #
 
-obj-y				+= dma-api.o dma-isa.o
+obj-y				+= dma-api.o
+obj-$(CONFIG_ISA_DMA_API)	+= dma-isa.o
 obj-$(CONFIG_SYSFS)		+= dma-sysfs.o
 obj-$(CONFIG_SH_DMA)		+= dma-sh.o
 obj-$(CONFIG_SH_DREAMCAST)	+= dma-pvr2.o dma-g2.o
-