cpufreq: arm_big_little: make vexpress driver depend on bL core driver

Currently vexpress big LITTLE driver selects ARM_BIG_LITTLE_CPUFREQ, so
if CONFIG_BIG_LITTLE isn't enabled and CONFIG_ARM_VEXPRESS_SPC_CPUFREQ
is enabled, we get the following build warnings:

warning: (ARM_VEXPRESS_SPC_CPUFREQ) selects ARM_BIG_LITTLE_CPUFREQ which has
unmet direct dependencies (ARCH_HAS_CPUFREQ && CPU_FREQ && (ARM || ARM64) && ARM
&& BIG_LITTLE && ARM_CPU_TOPOLOGY && HAVE_CLK)

To fix this, make ARM_VEXPRESS_SPC_CPUFREQ depend on ARM_BIG_LITTLE_CPUFREQ
instead of selecting it.

This also moves the entry for ARM_VEXPRESS_SPC_CPUFREQ along with other
big LITTLE config entries.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>