[ARM] Refine selection of ISA_DMA_API and generic dma.c code

ISA_DMA_API tells the rest of the kernel if the ISA DMA API is
available.  Select this symbol only on machine types which make
use of the ISA DMA API.

Make building of arch/arm/kernel/dma.c depend on this symbol -
if a machine does not support the ISA DMA API, it's pointless
building this file.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/Kconfig

@@ -154,6 +154,7 @@ config ARCH_RPC
 	select FIQ
 	select TIMER_ACORN
 	select ARCH_MAY_HAVE_PC_FDC
+	select ISA_DMA_API
 	help
 	  On the Acorn Risc-PC, Linux can support the internal IDE disk and
 	  CD-ROM interface, serial and parallel port, and the floppy drive.
@@ -206,6 +207,7 @@ config ARCH_IMX
 
 config ARCH_H720X
 	bool "Hynix-HMS720x-based"
+	select ISA_DMA_API
 	help
 	  This enables support for systems based on the Hynix HMS720x
 
@@ -290,12 +292,14 @@ config ISA
 	  (MCA) or VESA.  ISA is an older system, now being displaced by PCI;
 	  newer boards don't support it.  If you have ISA, say Y, otherwise N.
 
+# Select ISA DMA controller support
 config ISA_DMA
 	bool
+	select ISA_DMA_API
 
+# Select ISA DMA interface
 config ISA_DMA_API
 	bool
-	default y
 
 config PCI
 	bool "PCI support" if ARCH_INTEGRATOR_AP || ARCH_VERSATILE_PB

arch/arm/kernel/Makefile

@@ -6,11 +6,12 @@ AFLAGS_head.o := -DTEXT_OFFSET=$(TEXT_OFFSET)
 
 # Object file lists.
 
-obj-y		:= compat.o dma.o entry-armv.o entry-common.o irq.o \
+obj-y		:= compat.o entry-armv.o entry-common.o irq.o \
 		   process.o ptrace.o semaphore.o setup.o signal.o sys_arm.o \
 		   time.o traps.o
 
 obj-$(CONFIG_APM)		+= apm.o
+obj-$(CONFIG_ISA_DMA_API)	+= dma.o
 obj-$(CONFIG_ARCH_ACORN)	+= ecard.o 
 obj-$(CONFIG_FOOTBRIDGE)	+= isa.o
 obj-$(CONFIG_FIQ)		+= fiq.o