rtc: sun6i: disable automatic clock input switching

rtc: sun6i: disable automatic clock input switching

The V3(s) will detect a valid external low frequency clock and if it is
not present will automatically switch to the internal one. This might
hide bugs and (hardware) configuration errors. It's even worse because
the internal RTC runs significantly slower (32.000Hz vs 32.768Hz).
Fortunately for us, the V3(s) has an (undocumented) bypass of this
switching and the driver already supports it by setting the
.has_auto_swt flag.

Signed-off-by: Michael Walle <mwalle@kernel.org>
Acked-by: Chen-Yu Tsai <wens@csie.org>
Link: https://lore.kernel.org/r/20240730194905.2587202-1-mwalle@kernel.org
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>