ASoC: rsnd: src: Add SRC reset support for RZ/G3E

ASoC: rsnd: src: Add SRC reset support for RZ/G3E

The RZ/G3E SoC exposes a shared SCU reset controller used by all SRC
modules. Acquire it once and pass it through per-instance's
rsnd_mod_init() so it is wired into the rsnd_mod->rstc plumbing.

devm_reset_control_get_optional_shared() returns NULL when no reset
is described in DT, leaving existing R-Car generations unaffected.

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/20260525110230.4014435-17-john.madieu.xa@bp.renesas.com
Signed-off-by: Mark Brown <broonie@kernel.org>