msm: ipa: fix for de-framing error

De-framing logic relies on padding length provided by HW
for non-exception packets but computes it itself for
exception packets. Use the self computation scheme for
non-exception packets also. This works around an issue
where the header containing the padding length is missing
for non-exception packets in some cases

Change-Id: I18afd46c27ddff0291316b214e51785f1afe7562
Signed-off-by: Ravi Gummadidala <rgummadi@codeaurora.org>