arm, arm64: Select CONFIG_SCHED_THERMAL_PRESSURE

This option now correctly depends on CPU_FREQ_THERMAL, so select it on the
architectures that implement the required functions,
arch_set_thermal_pressure() and arch_get_thermal_pressure().

Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lkml.kernel.org/r/20200712165917.9168-4-valentin.schneider@arm.com