usbip: deletion of incorrect socket descriptor checking

This patch removes checking of socket descriptor value in daemons.

It was checked to be less than FD_SETSIZE(1024 usually) but it's not
correct.

To be exact, the maximum value of descriptor comes from
rlimit(RLIMIT_NOFILE).

Following kernel code determines the value :
    get_unused_fd_flags() : fs/files.c
    __alloc_fd() : fs/files.c
    expand_files() : fs/files.c

The defalut (soft limit) is defines as INR_OPEN_CUR(1024) in
include/linux/fs.h which is referenced form INIT_RLIMS in
include/asm-generic/resource.h. The value may be modified with ulimt,
sysctl, security configuration and etc.

With the kernel code above, when socket() system call returns positive
value, the value must be within rlimit(RLIMIT_NOFILE). No extra
checking is needed when socket() returns positive.

Without 'usbip: vhci number of ports extension' patch set, there's no
practical problem because of number of USB port restriction. With the
patch set, the value of socket descriptor can exceed FD_SETSIZE(1024
usually) if the rlimit is changed.
Signed-off-by: Nobuo Iwata <nobuo.iwata@fujixerox.co.jp>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

tools/usb/usbip/src/usbipd.c

@@ -398,13 +398,6 @@ static int listen_all_addrinfo(struct addrinfo *ai_head, int sockfdlist[],
 		 * (see do_standalone_mode()) */
 		usbip_net_set_v6only(sock);
 
-		if (sock >= FD_SETSIZE) {
-			err("FD_SETSIZE: %s: sock=%d, max=%d",
-			    ai_buf, sock, FD_SETSIZE);
-			close(sock);
-			continue;
-		}
-
 		ret = bind(sock, ai->ai_addr, ai->ai_addrlen);
 		if (ret < 0) {
 			err("bind: %s: %d (%s)",