Bluetooth: hci_ldisc: Free rw_semaphore on close

The percpu_rw_semaphore is not currently freed, and this leads to
a crash when the stale rcu callback is invoked.  DEBUG_OBJECTS
detects this.

 ODEBUG: free active (active state 1) object type: rcu_head hint: (null)
 ------------[ cut here ]------------
 WARNING: CPU: 1 PID: 2024 at debug_print_object+0xac/0xc8
 PC is at debug_print_object+0xac/0xc8
 LR is at debug_print_object+0xac/0xc8
 Call trace:
 [<ffffff80082e2c2c>] debug_print_object+0xac/0xc8
 [<ffffff80082e40b0>] debug_check_no_obj_freed+0x1e8/0x228
 [<ffffff8008191254>] kfree+0x1cc/0x250
 [<ffffff80083cc03c>] hci_uart_tty_close+0x54/0x108
 [<ffffff800832e118>] tty_ldisc_close.isra.1+0x40/0x58
 [<ffffff800832e14c>] tty_ldisc_kill+0x1c/0x40
 [<ffffff800832e3dc>] tty_ldisc_release+0x94/0x170
 [<ffffff8008325554>] tty_release_struct+0x1c/0x58
 [<ffffff8008326400>] tty_release+0x3b0/0x490
 [<ffffff80081a3fe8>] __fput+0x88/0x1d0
 [<ffffff80081a418c>] ____fput+0xc/0x18
 [<ffffff80080c0624>] task_work_run+0x9c/0xc0
 [<ffffff80080a9e24>] do_exit+0x24c/0x8a0
 [<ffffff80080aa4e0>] do_group_exit+0x38/0xa0
 [<ffffff80080aa558>] __wake_up_parent+0x0/0x28
 [<ffffff8008082c00>] el0_svc_naked+0x34/0x38
 ---[ end trace bfe08cbd89098cdf ]---

Signed-off-by: Hermes Zhang <chenhuiz@axis.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>