huashan: support mass storage USB modes

Change-Id: I2e3a6d65fb8ccd81259751b918edc4cbc056d956
Signed-off-by: Arnav Gupta <championswimmer@aokp.co>
huashan: allow external SD to be mounted as Mass Storage volume

Change-Id: Ied89d4ff0716cc2658f683d40b5b076e305a91f7
Signed-off-by: Arnav Gupta <championswimmer@aokp.co>