soc: renesas: Add support to read LSI DEVID register of RZ/G2{L,LC} SoC's

Add support for reading the LSI DEVID register which is present in
SYSC block of RZ/G2{L,LC} SoC's.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Biju Das <biju.das.jz@bp.renesas.com>
Link: https://lore.kernel.org/r/20210609163717.3083-3-prabhakar.mahadev-lad.rj@bp.renesas.com


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