omxaudioenc: Release baseaudioencoder stream lock while waiting for a buffer in ::handle_frame()
omxaudioenc: Release baseaudioencoder stream lock while waiting for a buffer in ::handle_frame()

This prevents deadlocks if no empty input buffers are available and
releasing input buffers requires the loop function to handle some
output buffers first.

RidgeRun/gst-omx,01org/gst-omx,renesas-devel/gst-omx,GStreamer/gst-omx,freedesktop-unofficial-mirror/gstreamer__gst-omx,renesas-rcar/gst-omx,freedesktop-unofficial-mirror/gstreamer__gst-omx,GStreamer/gst-omx,varunkumara/test-repo,surround-io/gst-omx,renesas-devel/gst-omx,tjormola/gst-omx,RidgeRun/gst-omx,CapOM/gst-omx,CapOM/gst-omx,varunkumara/test-repo,ismelykh/gst-omx-deinterlace,pliu6/gst-omx,zuh/gst-omx-rpi,GStreamer/gst-omx,varunkumara/test-repo,CapOM/gst-omx,xuguangxin/gst-omx,leio/gst-omx,01org/gst-omx,changzhix/gst-omx,leio/gst-omx,renesas-rcar/gst-omx,changzhix/gst-omx,xuguangxin/gst-omx,pliu6/gst-omx,surround-io/gst-omx,zuh/gst-omx-rpi,ismelykh/gst-omx-deinterlace,renesas-rcar/gst-omx,tjormola/gst-omx