usb: dwc3-msm: Add support for default none mode if extcon absent

On some platforms, the objective is to keep the controller in
'none' mode if it is dual role capable and extcon is absent. User
can later switch to required mode from userspace or via sysfs.
Add required support for default 'none' mode based on DT property
'qcom,default-mode-none'.

Change-Id: Icefee47a0a1a068a3c18f3a05593c883335a16b0
Signed-off-by: Ajay Agarwal <ajaya@codeaurora.org>