ARM: smp_twd: convert to use CLKSRC_OF init

Now that we have OF based init with CLKSRC_OF, convert smp_twd init
function to use it and covert all callers of
twd_local_timer_of_register.

Signed-off-by: Rob Herring <rob.herring@calxeda.com>
Cc: Shawn Guo <shawn.guo@linaro.org>
Cc: Sascha Hauer <kernel@pengutronix.de>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Viresh Kumar <viresh.linux@gmail.com>
Cc: Shiraz Hashim <shiraz.hashim@st.com>
Cc: Srinidhi Kasagar <srinidhi.kasagar@stericsson.com>
Cc: John Stultz <johnstul@us.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-omap@vger.kernel.org
Cc: spear-devel@list.st.com
Reviewed-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>