The dlfb_alloc_urb_list function is called in dlfb_usb_probe function,
after that if an error occurs, the dlfb_free_urb_list function need to
be called.

BUG: memory leak
unreferenced object 0xffff88810adde100 (size 32):
  comm "kworker/1:0", pid 17, jiffies 4294947788 (age 19.520s)
  hex dump (first 32 bytes):
    10 30 c3 0d 81 88 ff ff c0 fa 63 12 81 88 ff ff  .0........c.....
    00 30 c3 0d 81 88 ff ff 80 d1 3a 08 81 88 ff ff  .0........:.....
  backtrace:
    [<0000000019512953>] kmalloc include/linux/slab.h:552 [inline]
    [<0000000019512953>] kzalloc include/linux/slab.h:664 [inline]
    [<0000000019512953>] dlfb_alloc_urb_list drivers/video/fbdev/udlfb.c:1892 [inline]
    [<0000000019512953>] dlfb_usb_probe.cold+0x289/0x988 drivers/video/fbdev/udlfb.c:1704
    [<0000000072160152>] usb_probe_interface+0x177/0x370 drivers/usb/core/driver.c:396
    [<00000000a8d6726f>] really_probe+0x159/0x480 drivers/base/dd.c:554
    [<00000000c3ce4b0e>] driver_probe_device+0x84/0x100 drivers/base/dd.c:738
    [<00000000e942e01c>] __device_attach_driver+0xee/0x110 drivers/base/dd.c:844
    [<00000000de0a5a5c>] bus_for_each_drv+0xb7/0x100 drivers/base/bus.c:431
    [<00000000463fbcb4>] __device_attach+0x122/0x250 drivers/base/dd.c:912
    [<00000000b881a711>] bus_probe_device+0xc6/0xe0 drivers/base/bus.c:491
    [<00000000364bbda5>] device_add+0x5ac/0xc30 drivers/base/core.c:2936
    [<00000000eecca418>] usb_set_configuration+0x9de/0xb90 drivers/usb/core/message.c:2159
    [<00000000edfeca2d>] usb_generic_driver_probe+0x8c/0xc0 drivers/usb/core/generic.c:238
    [<000000001830872b>] usb_probe_device+0x5c/0x140 drivers/usb/core/driver.c:293
    [<00000000a8d6726f>] really_probe+0x159/0x480 drivers/base/dd.c:554
    [<00000000c3ce4b0e>] driver_probe_device+0x84/0x100 drivers/base/dd.c:738
    [<00000000e942e01c>] __device_attach_driver+0xee/0x110 drivers/base/dd.c:844
    [<00000000de0a5a5c>] bus_for_each_drv+0xb7/0x100 drivers/base/bus.c:431

Reported-by: syzbot+c9e365d7f450e8aa615d@syzkaller.appspotmail.com
Signed-off-by: Zqiang <qiang.zhang@windriver.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20201215063022.16746-1-qiang.zhang@windriver.com