power_supply: add HW_CURRENT_MAX power_supply property

Add support for HW_CURRENT_MAX property which returns maximum
input current that can be set for an adapter. This property will
be specifically used by parallel charger to cast an initial ICL
vote.

CRs-Fixed: 2014572
Change-Id: I49e80e6b25f40791d9035bc1567fdf881914b1e8
Signed-off-by: Ashay Jaiswal <ashayj@codeaurora.org>
Signed-off-by: Abhijeet Dharmapurikar <adharmap@codeaurora.org>
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>