clocksource/drivers/moxart: Plug memory and mapping leaks

If of_iomap() or any other subsequent function fails moxart_timer_init()
exits without freeing memory and unmapping the timer base.

Add proper cleanup points.

Signed-off-by: Sudip Mukherjee <sudip.mukherjee@codethink.co.uk>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Link: http://lkml.kernel.org/r/1482099996-1524-1-git-send-email-sudipm.mukherjee@gmail.com


Signed-off-by: Thomas Gleixner <tglx@linutronix.de>