microblaze: Remove duplicated prototype of start_thread()

The prototype for start_thread() is already present in the MMU/NOMMU
independent part of the file. Remove the duplicate.
Signed-off-by: Mathias Krause <minipli@googlemail.com>
Signed-off-by: Michal Simek <monstr@monstr.eu>

arch/microblaze/include/asm/processor.h

@@ -125,9 +125,6 @@ struct thread_struct {
 	.pgdir = swapper_pg_dir, \
 }
 
-/* Do necessary setup to start up a newly executed thread.  */
-void start_thread(struct pt_regs *regs,
-		unsigned long pc, unsigned long usp);
 
 /* Free all resources held by a thread. */
 extern inline void release_thread(struct task_struct *dead_task)