Timing function need Cycle Count Register CYCCNT of DWT,
but Arm-Cortex-M23 only support DWT_CTRL, DWT_PCSR and DWT_COMP
& DWT_FUNCTION registers. It can't meet the requirement of timing
function, so to remove CPU_CORTEX_M_HAS_DWT.
Signed-off-by: cyliang tw <cyliang@nuvoton.com>