avr32, exec: remove redundant set_fs(USER_DS)

The address limit is already set in flush_old_exec() so this
set_fs(USER_DS) is redundant.
Signed-off-by: Mathias Krause <minipli@googlemail.com>
Signed-off-by: Hans-Christian Egtvedt <hans-christian.egtvedt@atmel.com>

arch/avr32/include/asm/processor.h

@@ -131,7 +131,6 @@ struct thread_struct {
  */
 #define start_thread(regs, new_pc, new_sp)	 \
 	do {					 \
-		set_fs(USER_DS);		 \
 		memset(regs, 0, sizeof(*regs));	 \
 		regs->sr = MODE_USER;		 \
 		regs->pc = new_pc & ~1;		 \