ASoC: msm: qdsp6v2: set correct loopback mode

FM audio playback is failing as the loopback mode
is hardcoded to EC mode which is incorrect for
FM audio playback usecase.
Change it to default loopback mode.

Change-Id: I36b60ba2283b0bbe36f492e1410603b8c2050cc4
Signed-off-by: Shiv Maliyappanahalli <smaliyap@codeaurora.org>