um, 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>
Cc: Richard Weinberger <richard@nod.at>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/um/kernel/exec.c

@@ -38,7 +38,6 @@ void flush_thread(void)
 
 void start_thread(struct pt_regs *regs, unsigned long eip, unsigned long esp)
 {
-	set_fs(USER_DS);
 	PT_REGS_IP(regs) = eip;
 	PT_REGS_SP(regs) = esp;
 }