power: smb5: Add support for selecting secondary chargers

SM8150 platforms can be configured with SMB1355 and/or SMB1390 as
secondary charger(s). The main charger can enable secondary charger
via SMB_EN pin. The precedence of choosing secondary charger per
different power sources is as follows:

If HVDCP3 and PPS chargers are connected, SMB1390 (if present) is
preferred over SMB1355. For all other chargers (e.g. PD, HVDCP2,
DCP, OCP) SMB1355 is selected (if present).

Change-Id: I63c3cd54f934d1042b2191bf60add07c3442a76e
Signed-off-by: Harry Yang <harryy@codeaurora.org>