dt-bindings: mailbox: imx-mu: add i.MX93 S4 MU support

Similar to i.MX8ULP S4 MU, i.MX93 MU is dedicated for communication
between Sentinel and Cortex-A cores from hardware design, it could not be
reused for other purpose.

However i.MX93 S4 MU use separate tx/rx interrupt, so update
interrupts and add interrupt-names property.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>