ppc64: SPARSEMEM_VMEMMAP support

Enable virtual memmap support for SPARSEMEM on PPC64 systems.  Slice a 16th
off the end of the linear mapping space and use that to hold the vmemmap.
Uses the same size mapping as uses in the linear 1:1 kernel mapping.

[pbadari@gmail.com: fix warning]
Signed-off-by: Andy Whitcroft <apw@shadowen.org>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Badari Pulavarty <pbadari@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 037664d..5e001ad 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -295,6 +295,7 @@
 config ARCH_SPARSEMEM_ENABLE
 	def_bool y
 	depends on PPC64
+	select SPARSEMEM_VMEMMAP_ENABLE
 
 config ARCH_SPARSEMEM_DEFAULT
 	def_bool y