power: smb135x-charger: resolve circular wait between USB and SMB at probe

During SMB driver probe, it will wait for the usb_psy (the "USB" power
supply obejct) to be present before it creates a regulator. In host only
mode, USB will also try to get the regulator at probe time. This results
in a circular wait.

Update the SMB driver probe sequence so that the SMB driver does not wait
for the usb_psy in host only mode.

Change-Id: Ida8988a2ccff43124af6f3e61ee27b26f5c27169
CRs-fixed: 661326
Signed-off-by: Ke Liu <keliu@codeaurora.org>