libeffects: Corrected scratch memory size calculations

Corrected the scratch memory size calculations of bundle scratch for
floating point and multichannel builds.
Added comments detailing the usage and size calculation of
memories of various memories LVM.

Test: local native test (lvmtest)
Bug: 120874654
Change-Id: I69bb7faa106be5b82b4e579718afe0d1d3bb798d
1 file changed