clk: spear3xx: Use proper control register offset

commit 15ebb052 upstream.

The control register is at offset 0x10, not 0x0. This is wreckaged
since commit 5df33a62 (SPEAr: Switch to common clock framework).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Mike Turquette <mturquette@linaro.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>