powerpc: add context.vdso_base for 32-bit too

This adds a vdso_base element to the mm_context_t for 32-bit compiles
(both for ARCH=powerpc and ARCH=ppc).  This fixes the compile errors
that have been reported in arch/powerpc/kernel/signal_32.c.

Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/platforms/powermac/setup.c

@@ -458,7 +458,7 @@ static int pmac_pm_finish(suspend_state_t state)
 	printk(KERN_DEBUG "%s(%d)\n", __FUNCTION__, state);
 
 	/* Restore userland MMU context */
-	set_context(current->active_mm->context, current->active_mm->pgd);
+	set_context(current->active_mm->context.id, current->active_mm->pgd);
 
 	return 0;
 }