clk: renesas: rzv2h: Add instance field to struct pll

clk: renesas: rzv2h: Add instance field to struct pll

Add a two-bit "instance" member to struct pll and extend the PLL_PACK()
macro to accept an instance parameter.  Initialize all existing PLL
definitions with instance 0 to preserve legacy behavior. This change
enables support for SoCs with multiple PLL instances (for example,
RZ/G3E we have two PLL DSIs).

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://patch.msgid.link/20251015192611.241920-2-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>