[ARM] Hide ISA DMA API when ISA_DMA_API is unset

When ISA_DMA_API is unset, we're not implementing the ISA DMA API,
so there's no point in publishing the prototypes via asm/dma.h, nor
including the machine dependent parts of that API.

This allows us to remove a lot of mach/dma.h files which don't contain
any useful code.  Unfortunately though, some platforms put their own
private non-ISA definitions into mach/dma.h, so we leave these behind
and fix the appropriate #include statments.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/arch/arm/mach-pxa/dma.c b/arch/arm/mach-pxa/dma.c
index c0be17e..b1514fb 100644
--- a/arch/arm/mach-pxa/dma.c
+++ b/arch/arm/mach-pxa/dma.c
@@ -21,7 +21,7 @@
 #include <asm/system.h>
 #include <asm/irq.h>
 #include <mach/hardware.h>
-#include <asm/dma.h>
+#include <mach/dma.h>
 
 #include <mach/pxa-regs.h>