libeffects: Fix to resolve glitch with disabling LVCS

LVCS requires separate input and output buffers to process
stereo data out of multi channel audio.
In case of multi channel use case, actual number of inplace
scratch buffers required for LVCS module is 8. So, correct
the value of LVCS_SCRATCHBUFFERS to 8.

Test: Solotester
Bug: 132949357
Bug: 137835997

Change-Id: I27ad3d1a8e3b0f0ad32aaa538bf25850fb43ebe8