arm: kirkwood: add DT spi0 alias to LaCie boards

arm: kirkwood: add DT spi0 alias to LaCie boards

The spi0 alias is needed by the environment code to retrieve the SPI
flash. This patch adds some -u-boot.dtsi files, providing the spi0
aliases, for all the following Kirkwood-based LaCie boards:

- d2 Network v2
- Internet Space v2
- 2Big Network v2
- Network Space v2
- Network Space Lite v2
- Network Space Max v2
- Network Space Mini v2

Note that this -u-boot.dtsi files will be removed as soon as the spi0
aliases will be available in the upstream Linux dtsi files.

Signed-off-by: Simon Guinot <simon.guinot@sequanux.org>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Stefan Roese <sr@denx.de>
Reviewed-by: Jagan Teki <jagan@amarulasolutions.com>