Revert "ARM: 6944/1: mm: allow ASID 0 to be allocated to tasks"

This reverts commit 45b95235.

Will Deacon reports that:

 In 52af9c6c ("ARM: 6943/1: mm: use TTBR1 instead of reserved context ID")
 I updated the ASID rollover code to use only the kernel page tables
 whilst updating the ASID.

 Unfortunately, the code to restore the user page tables was part of a
 later patch which isn't yet in mainline, so this leaves the code
 quite broken.

We're also in the process of eliminating __ARCH_WANT_INTERRUPTS_ON_CTXSW
from ARM, so lets revert these until we can properly sort out what we're
doing with the context switching.
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

arch/arm/mm/context.c

@@ -93,7 +93,7 @@ static void reset_context(void *info)
 		return;
 
 	smp_rmb();
-	asid = cpu_last_asid + cpu;
+	asid = cpu_last_asid + cpu + 1;
 
 	flush_context();
 	set_mm_context(mm, asid);
@@ -143,13 +143,13 @@ void __new_context(struct mm_struct *mm)
 	 * to start a new version and flush the TLB.
 	 */
 	if (unlikely((asid & ~ASID_MASK) == 0)) {
-		asid = cpu_last_asid + smp_processor_id();
+		asid = cpu_last_asid + smp_processor_id() + 1;
 		flush_context();
 #ifdef CONFIG_SMP
 		smp_wmb();
 		smp_call_function(reset_context, NULL, 1);
 #endif
-		cpu_last_asid += NR_CPUS - 1;
+		cpu_last_asid += NR_CPUS;
 	}
 
 	set_mm_context(mm, asid);