olpc_battery: Add support for CURRENT_NOW and VOLTAGE_NOW

{CURRENT,VOLTAGE}_AVG are actually {CURRENT,VOLTAGE}_NOW (the EC code
directly passes through the value from the gas gauge instead of the
internally used average). We retain {CURRENT,VOLTAGE}_AVG as an alias
for compatibility reasons, it will be removed later.

Signed-off-by: Sascha Silbe <sascha-pgp@silbe.org>
[ pgf@laptop.org: added VOLTAGE_NOW, aliased to VOLTAGE_AVG ]
Signed-off-by: Paul Fox <pgf@laptop.org>
Signed-off-by: Anton Vorontsov <cbouatmailru@gmail.com>