ARM: renesas: Rename rmobile_get_prr() to renesas_get_prr()

Rename rmobile_get_prr() to renesas_get_prr() 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 '\<rmobile_get_prr\>' | \
  xargs -I {} sed -i 's@\<rmobile_get_prr\>@renesas_get_prr@g' {}
"

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