msm: camera: Fix camera crash when ctrl_q is empty

Add proper error condition if the list is empty and
return error value to upper layers instead of BUG_ON.

Change-Id: I89237e7a27d5fb1e1fd5f1a8a2dfd7ea9a1afff5
CRs-Fixed: 481759
Signed-off-by: Suresh Vankadara <svankada@codeaurora.org>