power_supply: add cycle_counts property

Currently, cycle_count and cycle_count_id are used to get the
cycle counter per SOC bucket. Add a string property cycle_counts
that can return all the cycle counters at once without the client
setting cycle_count_id.

Change-Id: If3014a4f865f94dc0895c1f5f7068ce936a0b62d
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>