bq2415x_charger: Add support for bq24157s

This patch adds bq24157s charger in the list of supported chargers.
bq24157s is similar to bq24158, except for Bit6 from Special Charger
Voltage/Enable Pin Status register, but this register is currently
not used by bq2415x_charger.

Signed-off-by: Anda-Maria Nicolae <anda-maria.nicolae@intel.com>
Signed-off-by: Sebastian Reichel <sre@kernel.org>