There was a corner case where the open slot count was going -ve indicating that there are no slots left for messaging. The current check to ensure non-zero messaging slots does not take that into account. This commit fixes that check. CRs-fixed: 370229 Change-Id: I832ce0a26f1919d3d03b4ef0311603a5a778685e Signed-off-by: Sagar Dharia <sdharia@codeaurora.org>