msm: ipa: fix the stats about tx packets using sw data path

The count needs to be bumped up after calling sps_transfer
and not upon getting callback for PKT_INIT immediate command.
This will provide information on how many sw tx packets are
not yet tx completed.

Change-Id: Ie05ee5c0e759e588547de4091dbf2d431ff50ef3
Signed-off-by: Ravi Gummadidala <rgummadi@codeaurora.org>