wlan: TX_Thread Spinng problem fix

If MGMT Q has pending frame, even AC Mask is DATA frames only,
WLANTL_GetFrames will retunr none 0 value.
This will make DXE indicate that DXE is out from low resource condition
and keep triggering to get frame from data Q.

Change-Id: I31e2d8f4fd1dd7e11d2ca705ee229db224ca2f05
CR-Fixed: 435323
(cherry picked from commit 7e48ca7b1f8054c33b0a8825367b7418e4ddc23e)