i2c: qcom: geni: Fix the way stretch stop is done

Currently when passing in the parameters for stretch stop when there isn't
a stretch we end up passing a mask that could affect other register bits.
Instead set the command parameter to 0 when stretch isn't being done.

Change-Id: I0c97ea4fd16f0ddb3dd5d53037c00c9bd3392bb0
Signed-off-by: Girish Mahadevan <girishm@codeaurora.org>