microblaze: remove unneeded variable 'err'

Fix the following coccicheck warning:
./arch/microblaze/kernel/signal.c:60:14-17: Unneeded variable: "err".
Return "0" on line 78

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>

arch/microblaze/kernel/signal.c

@@ -57,8 +57,6 @@ struct rt_sigframe {
 static int restore_sigcontext(struct pt_regs *regs,
 				struct sigcontext __user *sc, int *rval_p)
 {
-	unsigned int err = 0;
-
 #define COPY(x)		{err |= __get_user(regs->x, &sc->regs.x); }
 	COPY(r0);
 	COPY(r1);
@@ -75,7 +73,7 @@ static int restore_sigcontext(struct pt_regs *regs,
 
 	*rval_p = regs->r3;
 
-	return err;
+	return 0;
 }
 
 asmlinkage long sys_rt_sigreturn(struct pt_regs *regs)