Add convenience script for formatting a RPi SD card
Add convenience script for formatting a RPi SD card

I can never remember the command.

BUG=skia:

Review-Url: https://codereview.chromium.org/2082623002

google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot