powerpc: Stop using non-architected shared_proc field in lppaca

Although the shared_proc field in the lppaca works today, it is
not architected. A shared processor partition will always have a non
zero yield_count so use that instead. Create a wrapper so users
don't have to know about the details.

In order for older kernels to continue to work on KVM we need
to set the shared_proc bit. While here, remove the ugly bitfield.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
index 5850798..501e32c 100644
--- a/arch/powerpc/mm/numa.c
+++ b/arch/powerpc/mm/numa.c
@@ -1609,7 +1609,7 @@
 #endif
 		}
 	} else if (firmware_has_feature(FW_FEATURE_VPHN) &&
-		   get_lppaca()->shared_proc) {
+		   lppaca_shared_proc(get_lppaca())) {
 		if (!vphn_enabled) {
 			prrn_enabled = 0;
 			vphn_enabled = 1;