usbip: fix warning in vhci_hcd_probe/lockdep_init_map

usbip: fix warning in vhci_hcd_probe/lockdep_init_map

vhci_hcd calls sysfs_create_group() with dynamically allocated sysfs
attributes triggering the lock-class key not persistent warning. Call
sysfs_attr_init() for dynamically allocated sysfs attributes to fix it.

vhci_hcd vhci_hcd: USB/IP Virtual Host Controller
vhci_hcd vhci_hcd: new USB bus registered, assigned bus number 2
BUG: key ffff88006a7e8d18 not in .data!
------------[ cut here ]------------
WARNING: CPU: 0 PID: 1 at kernel/locking/lockdep.c:3131
lockdep_init_map+0x60c/0x770
DEBUG_LOCKS_WARN_ON(1)[    1.567044] Modules linked in:
CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.9.0-rc7+ #58
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
 ffff88006bce6eb8 ffffffff81f96c8a ffffffff00000a02 1ffff1000d79cd6a
 ffffed000d79cd62 000000046bce6ed8 0000000041b58ab3 ffffffff8598af40
 ffffffff81f969f8 0000000000000000 0000000041b58ab3 0000000000000200
Call Trace:
 [<     inline     >] __dump_stack lib/dump_stack.c:15
 [<ffffffff81f96c8a>] dump_stack+0x292/0x398 lib/dump_stack.c:51
 [<ffffffff812b808f>] __warn+0x19f/0x1e0 kernel/panic.c:550
 [<ffffffff812b8195>] warn_slowpath_fmt+0xc5/0x110 kernel/panic.c:565
 [<ffffffff813f3efc>] lockdep_init_map+0x60c/0x770 kernel/locking/lockdep.c:3131
 [<ffffffff819e43d4>] __kernfs_create_file+0x114/0x2a0 fs/kernfs/file.c:954
 [<ffffffff819e68f5>] sysfs_add_file_mode_ns+0x225/0x520 fs/sysfs/file.c:305
 [<     inline     >] create_files fs/sysfs/group.c:64
 [<ffffffff819e8a89>] internal_create_group+0x239/0x8f0 fs/sysfs/group.c:134
 [<ffffffff819e915f>] sysfs_create_group+0x1f/0x30 fs/sysfs/group.c:156
 [<ffffffff8323de24>] vhci_start+0x5b4/0x7a0 drivers/usb/usbip/vhci_hcd.c:978
 [<ffffffff82c907ca>] usb_add_hcd+0x8da/0x1c60 drivers/usb/core/hcd.c:2867
 [<ffffffff8323bc57>] vhci_hcd_probe+0x97/0x130
drivers/usb/usbip/vhci_hcd.c:1103
 ---
 ---
---[ end trace c33c7b202cf3aac8 ]---

Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>
Reported-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>