powerpc: Create arch/powerpc/platforms/iseries

I also move arch/ppc64/kernel/HvCall.c to
arch/powerpc/platforms/iseries/hvcall.c.

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
diff --git a/arch/powerpc/platforms/Makefile b/arch/powerpc/platforms/Makefile
index dbc0937..697adde 100644
--- a/arch/powerpc/platforms/Makefile
+++ b/arch/powerpc/platforms/Makefile
@@ -1,4 +1,5 @@
-obj-$(CONFIG_PPC_PMAC)	+= powermac/
-obj-$(CONFIG_4xx)	+= 4xx/
-obj-$(CONFIG_83xx)	+= 83xx/
-obj-$(CONFIG_85xx)	+= 85xx/
+obj-$(CONFIG_PPC_PMAC)		+= powermac/
+obj-$(CONFIG_4xx)		+= 4xx/
+obj-$(CONFIG_83xx)		+= 83xx/
+obj-$(CONFIG_85xx)		+= 85xx/
+obj-$(CONFIG_PPC_ISERIES)	+= iseries/