power: supply: bq257xx: Fix VSYSMIN clamping logic

power: supply: bq257xx: Fix VSYSMIN clamping logic

The minimal system voltage (VSYSMIN) is meant to protect the battery from
dangerous over-discharge. When the device tree provides a value for the
minimum design voltage of the battery, the user should not be allowed to
set a lower VSYSMIN, as that would defeat the purpose of this protection.

Flip the clamping logic when setting VSYSMIN to ensure that battery design
voltage is respected.

Cc: stable@vger.kernel.org
Fixes: 1cc017b7f9c7 ("power: supply: bq257xx: Add support for BQ257XX charger")
Tested-by: Chris Morgan <macromorgan@hotmail.com>
Signed-off-by: Alexey Charkov <alchark@flipper.net>
Link: https://patch.msgid.link/20260603-bq25792-v7-2-d487bed276d0@flipper.net
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>