arm: stm32mp: add CONFIG_STM32MP15_PWR

Add config CONFIG_STM32MP15_PWR to handle the
access to regulators managed by the PWR driver defined in
pwr_regulator.c

This driver is only used in U-Boot by STM32MP15x family.

Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Reviewed-by: Patrice Chotard <patrice.chotard@foss.st.com>
diff --git a/arch/arm/mach-stm32mp/Makefile b/arch/arm/mach-stm32mp/Makefile
index d362104..0ffec6e 100644
--- a/arch/arm/mach-stm32mp/Makefile
+++ b/arch/arm/mach-stm32mp/Makefile
@@ -21,5 +21,5 @@
 obj-$(CONFIG_TFABOOT) += boot_params.o
 endif
 
-obj-$(CONFIG_$(SPL_)DM_REGULATOR) += pwr_regulator.o
+obj-$(CONFIG_$(SPL_)STM32MP15_PWR) += pwr_regulator.o
 obj-$(CONFIG_OF_SYSTEM_SETUP) += fdt.o