tests: drivers: mbox: mbox_data: add support for s32z

The hardware MRU on SoC S32Z supports ping-pong data on a
MBOX channel within one core.

Added Kconfig TEST_SINGLE_CPU to enable test on single CPU  to wrap
the specific code for each testcase, As the expected received data
must match the sent data when running test single CPU. This differs
from the expected data in the current supported test transfer data
between 2 other cores, where the remote core increments the data by
one before transferring it back to the main core.

Signed-off-by: Cong Nguyen Huu <cong.nguyenhuu@nxp.com>