olpc_battery: Ensure that the TRICKLE bit is checked

There are times when the battery is present but trickle charging,
and the EC sets only the TRICKLE bit. So we must check for the bit
when we're checking the charging/present status.

Signed-off-by: Andres Salomon <dilinger@collabora.co.uk>
Signed-off-by: Anton Vorontsov <cbouatmailru@gmail.com>