Update peach_pit platform name to pit

Other platforms, like snow or spring, have a platform name
that is just the variant name. Updating peach_pit to be called
pit so scripts like chromeos-firmwareupdate correctly identify
the platform.

BUG=None
TEST=Run mosys and verify new name change

Change-Id: Ifc0cf8b34243cf7ffe2aca30084bc4bf55bfb1c2
Reviewed-on: https://gerrit.chromium.org/gerrit/61455
Reviewed-by: David Hendricks <dhendrix@chromium.org>
Commit-Queue: Katie Roberts-Hoffman <katierh@chromium.org>
Tested-by: Katie Roberts-Hoffman <katierh@chromium.org>
1 file changed