ARM: renesas: Rename ARCH_RMOBILE to ARCH_RENESAS

Rename ARCH_RMOBILE to ARCH_RENESAS because all the chips are made
by Renesas, while only a subset of them is from the R-Mobile
line.

Use the following command to perform the rename:

"
$ git grep -l 'ARCH_RMOBILE' | xargs -I {} sed -i 's@ARCH_RMOBILE@ARCH_RENESAS@g' {}
"

Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
Reviewed-by: Paul Barker <paul.barker.ct@bp.renesas.com>