ASoC: rsnd: fixup SCU_SYS_STATUSx access

SCU_SYS_STATUSx is the register that writing 1 initializes the bit,
and writing 0 is ignored. So, it should use rsnd_mod_write()
instead of rsnd_mod_bset(), otherwise all bit will be cleared.
Thanks Shimoda-san

Reported-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Mark Brown <broonie@kernel.org>