ASoC: msm: Fix playback failure on device switch during ULL playback

When a device switch happens for ultra low latency playback, we are
opening a regular playback COPP. ULL stream is routed to a non ULL
COPP. This results in playback failures.  ULL stream can be only
routed to a ULL COPP. The fix is to use the perf mode flag as a
part of front end instead of back end dai.

Change-Id: I07f3f02b1414d2826a2f2d3f79b1bc0337cd3c32
Signed-off-by: Krishnankutty Kolathappilly <kkolat@codeaurora.org>