powerpc: remove CONFIG_PPC_ISERIES from the architecture Kconfig files

After this, we can remove the legacy iSeries code more easily.

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index c713111..613eacf 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -614,7 +614,7 @@
 
 config ISA_DMA_API
 	bool
-	default !PPC_ISERIES || PCI
+	default PCI
 
 menu "Bus options"