ASoC: msm: add support for 256KHz ibit clock

The Low Power Audio Sub-System supports internal bit clock of
256KHz. Add definition for the same for use in audio use-cases.

Change-Id: Idc92595bab37548aa2b2936b57dd6605fae9a1ea
Signed-off-by: Banajit Goswami <bgoswami@codeaurora.org>