pollux: support mass storage USB modes

Change-Id: I9d7729feabb29f8a7f2eb12d850dec84124e6a50
Signed-off-by: Arnav Gupta <championswimmer@aokp.co>
pollux: allow external SD to be mounted as Mass Storage volume

Change-Id: I722ffa3f0697d0c1de79bcbc6388da0bb4cf14dc
Signed-off-by: Arnav Gupta <championswimmer@aokp.co>