arm: rmobile: Add basic R9A07G044L SoC support

Add a config option for the R9A07G044L SoC used in the RZ/G2L so that we
can make use of this in the subsequent driver patches.

Signed-off-by: Paul Barker <paul.barker.ct@bp.renesas.com>
Reviewed-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Marek Vasut <marek.vasut+renesas@mailbox.org>