clk: renesas: Introduce enum clk_reg_layout

From Linux v5.10-rc2, commit ffbf9cf3f946 by Yoshihiro Shimoda
Introduce enum clk_reg_layout to support multiple register layout variants

Signed-off-by: Hai Pham <hai.pham.ud@renesas.com>
Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>