msm: ipa: Fix to use after free issue

Added to code changes to ref_cnt variable will decrement only
when add_ref_hdr variable is true.

Change-Id: I0bcc3909669f4843c43135e5f047ac28fa62bb63
Acked-by: Ashok Vuyyuru <avuyyuru@qti.qualcomm.com>
Signed-off-by: Mohammed Javid <mjavid@codeaurora.org>