powerpc: Restore VDSO information on critical exception om BookE

Critical exception on 64-bit booke uses user-visible SPRG3 as scratch.
Restore VDSO information in SPRG3 on exception prolog.

Use a common sprg3 field in PACA for all powerpc64 architectures.

Signed-off-by: Mihai Caraman <mihai.caraman@freescale.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/arch/powerpc/kernel/vdso.c b/arch/powerpc/kernel/vdso.c
index b67db22..1b2076f 100644
--- a/arch/powerpc/kernel/vdso.c
+++ b/arch/powerpc/kernel/vdso.c
@@ -723,9 +723,7 @@
 
 	val = (cpu & 0xfff) | ((node & 0xffff) << 16);
 	mtspr(SPRN_SPRG3, val);
-#ifdef CONFIG_KVM_BOOK3S_HANDLER
-	get_paca()->kvm_hstate.sprg3 = val;
-#endif
+	get_paca()->sprg3 = val;
 
 	put_cpu();