soc: renesas: Add support for reading product revision for RZ/G2L family

As per RZ/G2L HW manual (Rev.1.00 Sep, 2021) DEV_ID [31:28] indicates
product revision. Use this information to populate the revision info
for RZ/G2L family.

Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Link: https://lore.kernel.org/r/20220121014117.21248-1-prabhakar.mahadev-lad.rj@bp.renesas.com


Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>