arm64: dts: s32g2: add serial/uart support

Add serial/uart support for NXP S32G2 based on the information provided by
NXP's CodeAurora BSP.

Signed-off-by: Larisa Grigore <larisa.grigore@nxp.com>
Signed-off-by: Chester Lin <clin@suse.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>