audioflinger: update multiplier logic to calculate frameCount

If the value of the multiplier used in calculating
mNormalFrameCount is odd, it is rounded off to a higher even value.

This results in an increase of mNormalFrameCount and thereby
the latency which is not expected.

Do not prefer an even multiplier and let the value remain as is
even if it is odd.

CRs-Fixed: 931454
Change-Id: Ia60d87d01caef6f45998bffeafc3d6a24f7c7fb4