staging: rtl8712: fix a potential memory leak in r871xu_drv_init()

In the Linux kernel, the following vulnerability has been resolved:

staging: rtl8712: fix a potential memory leak in r871xu_drv_init()

In r871xu_drv_init(), if r8712_init_drv_sw() fails, then the memory

allocated by r8712_alloc_io_queue() in r8712_usb_dvobj_init() is not

properly released as there is no action will be performed by

r8712_usb_dvobj_deinit().

To properly release it, we should call r8712_free_io_queue() in

r8712_usb_dvobj_deinit().

Besides, in r871xu_dev_remove(), r8712_usb_dvobj_deinit() will be called

by r871x_dev_unload() under condition `padapter->bup` and

r8712_free_io_queue() is called by r8712_free_drv_sw().

However, r8712_usb_dvobj_deinit() does not rely on `padapter->bup` and

calling r8712_free_io_queue() in r8712_free_drv_sw() is negative for

better understading the code.

So I move r8712_usb_dvobj_deinit() into r871xu_dev_remove(), and remove

r8712_free_io_queue() from r8712_free_drv_sw().