dt-bindings: mailbox: fsl,mu: add i.MX95 Generic/ELE/V2X MU compatible

Add i.MX95 Generic, Secure Enclave and V2X Message Unit compatible string.
And the MUs in AONMIX has internal RAMs for SCMI shared buffer usage.

Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Jassi Brar <jassisinghbrar@gmail.com>