arm, arm64: factorize common cpu capacity default code

arm and arm64 share lot of code relative to parsing CPU capacity
information from DT, using that information for appropriate scaling and
exposing a sysfs interface for chaging such values at runtime.

Factorize such code in a common place (driver/base/arch_topology.c) in
preparation for further additions.

Suggested-by: Will Deacon <will.deacon@arm.com>
Suggested-by: Mark Rutland <mark.rutland@arm.com>
Suggested-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juri Lelli <juri.lelli@arm.com>
Acked-by: Russell King <rmk+kernel@armlinux.org.uk>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>