sound: usb: Fix compilation error due to name change in qmi struct

Upstreamed qmi driver is using array_type as structure member name
in qmi_elem_info. Snapshot from msm-4.14 branch is using is_array
name.

Change-Id: I44d1147fb4dd6ae884fcc58155db7306ee9badea
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>