sdm: Donot override flush for virtual interface

On wfd pause, it is necessary to release all the pipes
connected on the wb interface. For this to happen,
a commit needs to be called informing the driver to
release all the pipes.
Hence, donot override flush for virtual interface so
that blank commit can be called as part of pause.

Change-Id: I2ef2cea2f31c0d23c6c027b37510a9faa196cc9a
2 files changed