x86/platform/olpc: Use a correct version when making up a battery node

The XO-1 and XO-1.5 batteries apparently differ in an ability to report
ambient temperature. We need to use a different compatible string for the
XO-1.5 battery.

Previously olpc_dt_fixup() used the presence of the battery node's
compatible property to decide whether the DT is up to date. Now we need
to look for a particular value in the compatible string, to decide

Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Acked-by: Pavel Machek <pavel@ucw.cz>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>