clk: renesas: rzg2l: Add rzg2l_mod_clock_init_mstop_helper()

clk: renesas: rzg2l: Add rzg2l_mod_clock_init_mstop_helper()

Refactor the mstop initialisation logic in rzg2l_mod_clock_init_mstop()
into a dedicated helper function rzg2l_mod_clock_init_mstop_helper().
This decouples the logic for setting module stop state on disabled
clocks from the iteration loop, allowing it to be reused during resume
to re-enable critical clocks.

No functional change.

Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Link: https://patch.msgid.link/20260324114329.268249-6-biju.das.jz@bp.renesas.com
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>