[PATCH][Bionic SRU] 2c: xlp9xx: Fix case where SSIF read transaction completes early

[Manoj Iyer]

Please consider the following SRU to bionic that fixes SSIF transaction
read issues on Cavium ThunderX2 (Sabers).

This patch was tested by me on a ThunderX2 Saber system with Bionic. I
used the ipmitool to generate a lot of data read, ran multiple instances
and found no read transaction issues with SSIF.