i2c-msm-v2: correct the scan algorithm

Applied correction to the scan algorithm including:
- remove stop tag after a write buffer which is not the last
  one for the message set.
- normalize the start is required boolean to 0 or one before
  it is used as an index to a lookup table.
- correct the detection condition for last buffer which is a
  rx.

Change-Id: Ide1eb4f63cb2950cfd6e402d961c63fae1dd2f21
Signed-off-by: Ankit Gupta <ankgupta@codeaurora.org>