Bluetooth: hci_ldisc: watchdog timeout while BT file transfer

Serial core's uart_write_wakeup( ) is used to unthrottle line
discipline to send more data notifying that there is less number
of data available in TTY circular buffer by MSM HSUART driver with
uart port spinlock acquire. Here serial core is calling
HCI Line Discipline driver's hci_uart_tty_wakeup( ) without scheduling
tasklet in 3.4 kernel compare to 3.0 kernel. Due to that HCI
Line Discipline driver pushes all available data to TTY Core as part of
hardirq context in 3.4 kernel compare to softirq context on 3.0 kernel,
which is causing watchdog timeout issue. Hence move all
hci_uart_tty_wakeup() work to tasklet context to resolve this issue.

Change-Id: If829b85e97aa9439e6e2c67ab6278c847aa81927
Signed-off-by: Ram Mohan Korukonda <rkorukon@codeaurora.org>