ARM: SA1100: Create dummy clk_get_rate() to avoid build failures

ARM: SA1100: Create dummy clk_get_rate() to avoid build failures

There are some parts of common kernel which would be using routines
like clk_get_rate() on some platforms. Currently, they wouldn't be
called for SA1100 boards, but they are needed for successful kernel
compilation.

Create a dummy clk_get_rate() routine for SA1100 which can be called
by the cpufreq core. More dummy routines might be added later if
necessary.

Cc: Russell King <linux@arm.linux.org.uk>
Cc: Arnd Bergmann <arnd.bergmann@linaro.org>
Reported-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
[rjw: Changelog]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>