Having sgtl5000_clk defines as "fixed-clock" is not enough to prevent
the dai subsystem from overwriting the frequency via sgtl5000_set_dai_sysclk.

Setting system-clock-fixed does the job, and now a 1kHz sine wave
comes out as actually 1kHz, no matter the sample rate of the source.

Testcase: These should sound the same:

 speaker-test -r 48000 -t sine -f 1000
 speaker-test -r 24000 -t sine -f 1000

Also remove the clock link here as having it in sgtl5000 and
sgtl5000_codec causes duplicate clock unprepares with associated
backtrace.

Cc: stable@vger.kernel.org
Fixes: c484cf93 ("arm64: dts: rockchip: add PX30-µQ7 (Ringneck) SoM with Haikou baseboard")
Signed-off-by: Jakob Unterwurzacher <jakob.unterwurzacher@theobroma-systems.com>
Link: https://lore.kernel.org/r/20230907151725.198347-2-jakob.unterwurzacher@theobroma-systems.comSigned-off-by: Heiko Stuebner <heiko@sntech.de>