ASoC: msm: Add Slimbus6 playback dai-link

Add slimbus6 playback back-end dai-link on msmcobalt
platform with wcd934x audio codec. This dai-link enables
audio playback over headphones.

Change-Id: I83c2291909bda2473d7d0b3147b4a0244f7450b0
Signed-off-by: Phani Kumar Uppalapati <phaniu@codeaurora.org>