drivers: char: tlclk.c: Avoid data race between init and interrupt handler

drivers: char: tlclk.c: Avoid data race between init and interrupt handler

After registering character device the file operation callbacks can be
called. The open callback registers interrupt handler.
Therefore interrupt handler can execute in parallel with rest of the init
function. To avoid such data race initialize telclk_interrupt variable
and struct alarm_events before registering character device.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>
Link: https://lore.kernel.org/r/20200417153451.1551-1-madhuparnabhowmik10@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>