config: add atomic cpu to X86_MESI_CMP_directory build options

config: add atomic cpu to X86_MESI_CMP_directory build options
There is some problem with the way listing cpu options right now.
Since Ruby uses the options variable, this variable has to be created in the
config file that runs the fs test for x86 and mesi cmp directory combination.
While creating the variable, some error is occurs due to the way list of cpu
types is now created. Hence, we need to compile all the cpu models.