powerpc: select HAVE_CONTEXT_TRACKING for pSeries

Start context tracking support from pSeries.
Signed-off-by: Li Zhong <zhong@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/platforms/pseries/Kconfig

@@ -18,6 +18,7 @@ config PPC_PSERIES
 	select PPC_PCI_CHOICE if EXPERT
 	select ZLIB_DEFLATE
 	select PPC_DOORBELL
+	select HAVE_CONTEXT_TRACKING
 	default y
 
 config PPC_SPLPAR