arm64: dts: s32g3: Add the Software Timer Watchdog (SWT) nodes

Referred in the documentation as the Software Timer Watchdog (SWT),
the s32g3 has 12 watchdogs. The number of watchdogs is designed to
allow dedicating one watchdog per Cortex-M7/A53 present on the SoC.

Add the SWT nodes in the device tree.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Ghennadi Procopciuc <ghennadi.procopciuc@nxp.com>
Cc: Thomas Fossati <thomas.fossati@linaro.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>