kgdboc: reset input devices (keyboards) when exiting debugger

Use the newly exported input_reset_device() call to reset LED state and
mark all keys/buttons as released on all keyboard-like devices when
exiting the debugger.

[jason.wessel@windriver.com: fix compile without keyboard input driver]
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>