msm: tspp: fix sps notification frequency

TSPP driver marks descriptors for notification by setting the
SPS_IOVEC_FLAG_INT flag. However, SPS driver seems to issue a
notification if this flag is set or if user data pointer was provided.
To avoid notification on every descriptor, pass user data pointer
only on descriptors with the flag set.

Change-Id: I718720bc7ebbb1b2a4ee181531d3449b8436c906
Signed-off-by: Gilad Broner <gbroner@codeaurora.org>