selftests/resctrl: Remove duplicate feature check from CMT test

The test runner run_cmt_test() in resctrl_tests.c checks for CMT
feature and does not run cmt_resctrl_val() if CMT is not supported.
Then cmt_resctrl_val() also check is CMT is supported.

Remove the duplicated feature check for CMT from cmt_resctrl_val().

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Tested-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
Reviewed-by: Reinette Chatre <reinette.chatre@intel.com>
Reviewed-by: Shaopeng Tan <tan.shaopeng@jp.fujitsu.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>