ASoC: msm8x16-wcd: increase ref buffer current of OPAMP

In tombak codec, TX degradation issue is seen on TSMC
parts. The present setting of reference buffer current
of 0.5uA is making the reference buffer too slow and
it is not able to keep the reference voltage fixed.
Consequently, noise folding and noise shaping degradation
is seen. Increase the ADC REF Bias to address this issue.

CRs-Fixed: 762776
Change-Id: Iddc953805ea8d278386be906593f0037c028d0cf
Signed-off-by: Laxminath Kasam <lkasam@codeaurora.org>