ASoC: msm: fix a use after free problem in audio_calibration

An index variable was used to access an array, which could cause
invalid memory accesses, especially when SLUB debug is enabled.

Change-Id: Ic0ba2a6f500a97ecdd8277fcbd313ecd6777934b
Signed-off-by: Jeremy Gebben <jgebben@codeaurora.org>