boards: s32z270dc2_r52: support board revision D

Add a board revision D for the s32z270dc2_r52 boards and make the
existing revision B the default. The main difference between these
revisions affecting current Zephyr port is the USB/UART port that
was moved from LINFlexD instance 0 to 9.

Signed-off-by: Manuel Argüelles <manuel.arguelles@nxp.com>