power: supply: ab8500: Set typing and props

I had the following weird phenomena on a mobile phone: while
the capacity in /sys/class/power_supply/ab8500_fg/capacity
would reflect the actual charge and capacity of the battery,
only 1/3 of the value was shown on the battery status
indicator and warnings for low battery appeared.

It turns out that UPower, the Freedesktop power daemon,
will average all the power supplies of type "battery" in
/sys/class/power_supply/* if there is more than one battery.

For the AB8500, there was "battery" ab8500_fg, ab8500_btemp
and ab8500_chargalg. The latter two don't know anything
about the battery, and should not be considered. They were
however averaged and with the capacity of 0.

Flag ab8500_btemp and ab8500_chargalg with type "unknown"
so they are not averaged as batteries.

Remove the technology prop from ab8500_btemp as well, all
it does is snoop in on knowledge from another supply.

After this the battery indicator shows the right value.

Cc: Stefan Hansson <newbyte@disroot.org>
Cc: stable@vger.kernel.org
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>