Add 1v1, 1v8 and 3v3 PWR regulators on stm32mp131. Temporary add them as fixed regulators, waiting for full SCMI regulators support. This is a precursor patch to enable USB support on STM32MP13. Note: USB support requires these regulators to be enabled before entering kernel. Signed-off-by: Fabrice Gasnier <fabrice.gasnier@foss.st.com> Signed-off-by: Alexandre Torgue <alexandre.torgue@foss.st.com>