phy: msm: usb: Fix notification of charging current in SDP

As a part of notifying charger current to power supply, we first
set POWER_SUPPLY_PROP_ONLINE property which may not be supported
resulting in error path and SDP_CURRENT_MAX property not being
set at all. Fix this by not setting ONLINE property. Also,
refactor the code to vote for charging current only in SDP mode.

Change-Id: I3be76ea6185070fa06c8e944878f84d61cb2a3e9
Signed-off-by: Ajay Agarwal <ajaya@codeaurora.org>