Hi Waqas,
CUCM11.5(1)SU1 (i.e. 11.5.1.11900-26) comes with TSP version 11.5.1.2-0, while 11.5(1)SU2 comes with TSP version 11.5.1.4-0. so after upgrading to SU2 you need to upgrade the TSP plugin in order to avoid any issue.
P.S. having different TSP/ CUCM versions may work, but will not be fully be supported.
plugin details can be found in readme files for each CUCM release:
11.5(1)SU1: http://www.cisco.com/web/software/282074295/134530/cucm-readme-1151su1-Rev3.pdf
11.5(1)SU2: http://www.cisco.com/web/software/282074295/136664/cucm-readme-1151su2.pdf
Thank you,
Shadi