power: supply: qcom_battmgr: clamp charge control thresholds

power: supply: qcom_battmgr: clamp charge control thresholds

The sysfs API documentation says that drivers "round written values to
the nearest supported value" for charge_control_end_threshold.

Let's do this for both thresholds, as userspace (e.g. upower) generally
does not expect these writes to fail at all.

Fixes: cc3e883a0625 ("power: supply: qcom_battmgr: Add charge control support")
Signed-off-by: Val Packett <val@packett.cool>
Link: https://patch.msgid.link/20251012233333.19144-3-val@packett.cool
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>