[ Upstream commit 8314c212 ]

the charging current uses unsigned int variables, if we step back
if the current is still low, we would run into negative which
means setting the target to a huge value.
Better add checks here.
Signed-off-by: Andreas Kemnade <andreas@kemnade.info>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>