microblaze: Remove __ARCH_WANT_INTERRUPTS_ON_CTXSW usage

As far as I can tell the only reason microblaze has
__ARCH_WANT_INTERRUPTS_ON_CTXSW is because it initializes new task state
with interrupts enabled so that on switch_to() interrupts get enabled.

So change copy_thread() to clear MSR_IE instead of set it, this will
ensure switch_to() will always keep IRQs disabled.

The scheduler will disable IRQs when taking rq->lock in schedule() and
enable IRQs in finish_lock_switch() after its done its magic.

This leaves ARM the only __ARCH_WANT_INTERRUPTS_ON_CTXSW user.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Michal Simek <monstr@monstr.eu>

arch/microblaze/include/asm/system.h

@@ -17,8 +17,6 @@
 #include <asm-generic/cmpxchg.h>
 #include <asm-generic/cmpxchg-local.h>
 
-#define __ARCH_WANT_INTERRUPTS_ON_CTXSW
-
 struct task_struct;
 struct thread_info;
 

arch/microblaze/kernel/process.c

@@ -179,6 +179,7 @@ int copy_thread(unsigned long clone_flags, unsigned long usp,
 
 	ti->cpu_context.msr = (childregs->msr|MSR_VM);
 	ti->cpu_context.msr &= ~MSR_UMS; /* switch_to to kernel mode */
+	ti->cpu_context.msr &= ~MSR_IE;
 #endif
 	ti->cpu_context.r15 = (unsigned long)ret_from_fork - 8;