tests: Revert "libs2/tf: Fix a/z/c/z/z/s/l/z/T/cmock submodule to v2.5.3-g9d092898" SiliconLabsSoftware#60

This reverts commit 9865caa.

Bug: SiliconLabsSoftware#46
Origin: SiliconLabsSoftware#36
Signed-off-by: Philippe Coval <[email protected]>

Author: rzr