FRV: Fix the preemption handling

Fix the preemption handling in FRV code where the PREEMPT_ACTIVE value is
incorrectly loaded into the threadinfo flags rather than the threadinfo
preemption count.

Unfortunately, the code cannot be simply converted to use
preempt_schedule_irq() as is because FRV uses virtual interrupt disablement to
cut down on the cost of actually disabling interrupts and thus
local_irq_enable() doesn't actually enable interrupts.

Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Al Viro <viro@ZenIV.linux.org.uk>

arch/frv/kernel/entry.S

@@ -1086,7 +1086,7 @@ __entry_preempt_need_resched:
 	beq		icc0,#1,__entry_return_direct
 
 	setlos		#PREEMPT_ACTIVE,gr5
-	sti		gr5,@(gr15,#TI_FLAGS)
+	sti		gr5,@(gr15,#TI_PRE_COUNT)
 
 	andi		gr23,#~PSR_PIL,gr23
 	movgs		gr23,psr