power: qpnp-smb2: Force power-role to UFP by default

Add a DT property "qcom,ufp-only-mode" which forces power-role
to UFP during initialization. A role swap to DFP is not allowed
if this property is defined.

Change-Id: Id21876473ca16ea007e353b3ce84637f9f489b19
Signed-off-by: Kavya Nunna <knunna@codeaurora.org>