[media] em28xx-audio: flush work at .fini
[media] em28xx-audio: flush work at .fini

As a pending action might be still there at the work
thread, flush it.

Signed-off-by: Mauro Carvalho Chehab <0cae1d1e981e84d16b82ca3d17be8a7f826608d3@samsung.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs