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

There is a slew of defines, structs and enums and even a
function call only relevant for the charging code that
still lives in <linux/mfd/abx500.h>. Push it down to the
"ab8500-bm.h" header in the power supply subsystem where
it is actually used.

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>