mfd/power: ab8500: Push algorithm to power supply code

The charging algorithm header is only used locally in the
power supply subsystem so push this down into
drivers/power/supply and rename from the confusing
"ux500_chargalg.h" to "ab8500-chargalg.h" for clarity:
it is only used with the AB8500.

This is another remnant of non-DT code needing to pass
data from boardfiles, which we don't do anymore.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>