dt-bindings: rcc: stm32: add STM32MP13 SCMI regulators IDs

Adds SCMI regulator identifiers for STM32MP13x family.

Signed-off-by: Etienne Carriere <etienne.carriere@foss.st.com>
Signed-off-by: Pascal Paillet <p.paillet@foss.st.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Alexandre Torgue <alexandre.torgue@foss.st.com>