stm32mp1: activate FIXED regulator

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
diff --git a/configs/stm32mp15_basic_defconfig b/configs/stm32mp15_basic_defconfig
index 87f60be..c72a440 100644
--- a/configs/stm32mp15_basic_defconfig
+++ b/configs/stm32mp15_basic_defconfig
@@ -37,6 +37,7 @@
 # CONFIG_SPL_PMIC_CHILDREN is not set
 CONFIG_PMIC_STPMU1=y
 CONFIG_DM_REGULATOR=y
+CONFIG_DM_REGULATOR_FIXED=y
 CONFIG_DM_REGULATOR_GPIO=y
 CONFIG_DM_REGULATOR_STM32_VREFBUF=y
 CONFIG_DM_REGULATOR_STPMU1=y