Revert "power: supply: sbs-battery: add PEC support"

This depends on the simplification of sbs_read_string_data, which
breaks booting exynos5 based chromebooks. More investigation is
required, so this patch and the simplification patch are reverted
for this merge window.

Note, that this is only a partial revert, since sbs_update_presence()
has not been removed. It is also required for the charger broadcast
disabling.

This reverts commit 79bcd5a4.

Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>