cpufreq: make schedutil the default for arm and arm64

schedutil is already a hard-requirement for EAS, which has lead to making
it default on arm (when CONFIG_BIG_LITTLE), see:

  commit 8fdcca8e ("cpufreq: Select schedutil when using big.LITTLE")

One thing worth pointing out is that schedutil isn't only relevant for
asymmetric CPU capacity systems; for instance, schedutil is the only
governor that honours util-clamp performance requests. Another good example
of this is x86 switching to using it by default in:

  commit a00ec387

 ("cpufreq: intel_pstate: Select schedutil as the default governor")

Arguably it should be made the default for all architectures, but it seems
better to wait for them to also gain frequency invariance powers. Make it
the default for arm && arm64 for now.

Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Ionela Voinescu <ionela.voinescu@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>