ppc64_cpu: display error message after set_smt_state_one failure
ppc64_cpu: display error message after set_smt_state_one failure

This avoids a silent error if threads are unable to be onlined or offlined.

Signed-off-by: Thomas Falcon <3be58c5f4f5b8a6fb702b2062dd3fbac29655c50@linux.vnet.ibm.com>

shenki/powerpc-utils,shenki/powerpc-utils,shenki/powerpc-utils