At least for 4430, trying to use the single conversion mode eventually
hangs the thermal sensor. This can be quite easily seen with errors:

thermal thermal_zone0: failed to read out thermal zone (-5)

Also, trying to read the temperature shows a stuck value with:

$ while true; do cat /sys/class/thermal/thermal_zone0/temp; done

Where the temperature is not rising at all with the busy loop.

Additionally, the EOCZ (end of conversion) bit is not rising on 4430 in
single conversion mode while it works fine in continuous conversion mode.
It is also possible that the hung temperature sensor can affect the
thermal shutdown alert too.

Let's fix the issue by adding TI_BANDGAP_FEATURE_CONT_MODE_ONLY flag and
use it for 4430.

Note that we also need to add udelay to for the EOCZ (end of conversion)
bit polling as otherwise we have it time out too early on 4430. We'll be
changing the loop to use iopoll in the following clean-up patch.

Cc: Adam Ford <aford173@gmail.com>
Cc: Carl Philipp Klemm <philipp@uvos.xyz>
Cc: Eduardo Valentin <edubezval@gmail.com>
Cc: H. Nikolaus Schaller <hns@goldelico.com>
Cc: Merlijn Wajer <merlijn@wizzup.org>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: Peter Ujfalusi <peter.ujfalusi@gmail.com>
Cc: Sebastian Reichel <sre@kernel.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Tested-by: Adam Ford <aford173@gmail.com> #logicpd-torpedo-37xx-devkit
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20210205134534.49200-3-tony@atomide.com