clocksource/drivers/mtk_timer: Fix pr_warn() messages in mtk_timer_init

1) Change pr_warn()s to pr_err()s. These messages are actually errors and not
   warnings.
2) Add missing \n.
3) Error message for kzalloc() failure is removed per suggestion by Joe Perches.
   There is generic stack_dump() for allocation issues.

Signed-off-by: Alexey Klimov <alexey.klimov@linaro.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>