cpufreq: vexpress: Drop unused variable

arm:allmodconfig fails to build with the following error.

drivers/cpufreq/vexpress-spc-cpufreq.c:454:13: error:
					unused variable 'cur_cluster'

Remove the unused variable.

Fixes: bb8c26d9 ("cpufreq: vexpress: Set CPUFREQ_IS_COOLING_DEV flag")
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>