arm64: dts: juno: add cpu capacity-dmips-mhz information to R2 boards

This patch adds cpu capacity-dmips-mhz information to Juno R2 boards.

Cc: Rob Herring <robh+dt@kernel.org>
Cc: Pawel Moll <pawel.moll@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Ian Campbell <ijc+devicetree@hellion.org.uk>
Cc: Kumar Gala <galak@codeaurora.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Liviu Dudau <Liviu.Dudau@arm.com>
Cc: Sudeep Holla <sudeep.holla@arm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Jon Medhurst <tixy@linaro.org>
Cc: Olof Johansson <olof@lixom.net>
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: devicetree@vger.kernel.org
Signed-off-by: Juri Lelli <juri.lelli@arm.com>
[sudeep.holla@arm.com: reformated subject and updated changelog]
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>