tty: Use spin_lock_irq() for ctrl_lock when interrupts enabled

Interrupts are enabled in the n_tty_read() loop, ioctl(TIOCPKT)
and pty driver flush_buffer() routine; no need to save and restore
local interrupt state.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Reviewed-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --cc drivers/tty/n_tty.c
Simple merge

diff --cc drivers/tty/pty.c
Simple merge