input: touchscreen: fts: Call touch event callback on every event

Call the touch event callback on every event received.  The previous
design call the callback after processing the entire FIFO.  However,
there are chances where multiple events with the same FID exist in
the FIFO.  This will cause the previous event to over-written
causing lost event.

Change-Id: I650edbb3a56243e091da6b5c6a9d47330ce37d65
Signed-off-by: Rick Huang <rhuang@codeaurora.org>