usb: dwc3: otg: Don't abort otg_init() if otg is not supported

If hardware doesn't support OTG, continue with otg_init() as
currently there is no only device mode support available.
Aborting otg_init() would crash device due to NULL dereference
in dwc3_msm probe.

Change-Id: I1273a58acf319b64c1ceaf41134f59cc59d5bdcd
Signed-off-by: Mayank Rana <mrana@codeaurora.org>