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: I5ef968d02b9292eb6779615ee3cc8edc6ac13c3a
Signed-off-by: Ajay Agarwal <ajaya@codeaurora.org>
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>