ASoC: rsnd: src: Acquire shared SCU clocks for RZ/G3E

ASoC: rsnd: src: Acquire shared SCU clocks for RZ/G3E

The RZ/G3E SoC requires explicit SCU (Sampling Rate Converter Unit)
clock management:

 - scu:        SCU top-level module clock (CPG_CLKON_15.CLK6_ON)
 - scu_x2:     SCU top-level double-rate clock (CPG_CLKON_15.CLK7_ON)
 - scu_supply: SCU register-access / housekeeping clock
               (CPG_CLKON_23.CLK14_ON)

Without every one of them enabled, no SCU register is reachable.

Hold these in a new struct rsnd_src_ctrl and acquire them with
devm_clk_get_optional_enabled(). scu_supply is intentionally left
untouched by the system suspend/resume path added later in the
series, so SCU registers stay reachable across PM transitions.

Signed-off-by: John Madieu <john.madieu.xa@bp.renesas.com>
Acked-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Link: https://patch.msgid.link/20260525110230.4014435-16-john.madieu.xa@bp.renesas.com
Signed-off-by: Mark Brown <broonie@kernel.org>