power_supply: Increment power supply use counter when obtaining references

Increment the power_supply.use_cnt usage counter on:
 - power_supply_get_by_phandle()
 - power_supply_get_by_name()
and decrement it on power_supply_put() call.

This helps tracking of valid usage of power supply instance by
consumers. The usage counter itself also allows safe calling of
power_supply_get_property-like functions even when driver unregisters
this power supply.

Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Reviewed-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Sebastian Reichel <sre@kernel.org>