um: Remove the unneeded result variable

Return the value epoll_ctl() directly instead of storing it in another
redundant variable.
Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: ye xingchen <ye.xingchen@zte.com.cn>
Signed-off-by: Richard Weinberger <richard@nod.at>

arch/um/os-Linux/irq.c

@@ -127,12 +127,10 @@ int os_mod_epoll_fd(int events, int fd, void *data)
 int os_del_epoll_fd(int fd)
 {
 	struct epoll_event event;
-	int result;
 	/* This is quiet as we use this as IO ON/OFF - so it is often
 	 * invoked on a non-existent fd
 	 */
-	result = epoll_ctl(epollfd, EPOLL_CTL_DEL, fd, &event);
-	return result;
+	return epoll_ctl(epollfd, EPOLL_CTL_DEL, fd, &event);
 }
 
 void os_set_ioignore(void)