Extend the default kernel command line for Gray Hawk Single for mounting
the root filesystem via NFS, like is done for all other Renesas
development boards.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/0c291919071350674648317f8cf3efbd1ca4475f.1712068442.git.geert+renesas@glider.be