i386: fix CPU hotplug with 2GB VMSPLIT

In VMSPLIT mode, kernel PGD might have more entries than user space
Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Adrian Bunk <bunk@stusta.de>

arch/i386/kernel/smpboot.c

@@ -1054,7 +1054,7 @@ int __devinit smp_prepare_cpu(int cpu)
 
 	/* init low mem mapping */
 	clone_pgd_range(swapper_pg_dir, swapper_pg_dir + USER_PGD_PTRS,
-			KERNEL_PGD_PTRS);
+			min_t(unsigned long, KERNEL_PGD_PTRS, USER_PGD_PTRS));
 	flush_tlb_all();
 	schedule_work(&task);
 	wait_for_completion(&done);