s390: convert release_thread() into a static inline function

release_thread() is an empty function that gets called on every task
exit. Move the function to a header file and force inlining of it, so
that the compiler can optimize it away instead of generating a
pointless function call.
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/processor.h

@@ -218,7 +218,7 @@ void show_registers(struct pt_regs *regs);
 void show_cacheinfo(struct seq_file *m);
 
 /* Free all resources held by a thread. */
-extern void release_thread(struct task_struct *);
+static inline void release_thread(struct task_struct *tsk) { }
 
 /* Free guarded storage control block for current */
 void exit_thread_gs(void);

arch/s390/kernel/process.c

@@ -58,10 +58,6 @@ void flush_thread(void)
 {
 }
 
-void release_thread(struct task_struct *dead_task)
-{
-}
-
 void arch_release_task_struct(struct task_struct *tsk)
 {
 }