power: qpnp-smbcharger: add present property to dc psy

Currently, the get property function of the DC power supply supports
POWER_SUPPLY_PROP_PRESENT, but the DC power supply does not export it
as one of the available properties. Fix this by adding present to the
exported properties list.

CRs-Fixed: 712783
Change-Id: I3463fe6844de6ee28d77ee21e33236c9a6731163
Signed-off-by: Xiaozhe Shi <xiaozhes@codeaurora.org>