CLOCKSOURCE: mips-gic-timer: Ensure GIC counter is running

CLOCKSOURCE: mips-gic-timer: Ensure GIC counter is running

Start the GIC counter after configuring the clocksource since there
are no guarantees the counter will be running after a CPU reset.

Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/9595/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>