sched/x86: Make CONFIG_SCHED_MC_PRIO=y easier to enable

Right now CONFIG_SCHED_MC_PRIO has X86_INTEL_PSTATE as a dependency,
which is not enabled by default and which hides the CONFIG_SCHED_MC_PRIO
hardware-enabling feature.

Select X86_INTEL_PSTATE instead, plus its dependency (CPU_FREQ), if the
user enables CONFIG_SCHED_MC_PRIO=y.

(Also align the CONFIG_SCHED_MC_PRIO Kconfig help text in standard style.)

Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: bp@suse.de
Cc: jolsa@redhat.com
Cc: linux-acpi@vger.kernel.org
Cc: linux-pm@vger.kernel.org
Cc: rjw@rjwysocki.net
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>