dts/arm: Add the 3 MEC1501 basic timer instances.

4 are found: 2 with a counter of 16bits and 2 with a counter of 32 bits.
However, first 32bits instance will not be exposed as it will be used by
rtos timer driver directly to implement k_busy_wait()

Signed-off-by: Tomasz Bursztyka <tomasz.bursztyka@linux.intel.com>