ARM: stm32: Factor out save_boot_params

The STM32MP15xx platform currently comes with two incompatible
implementations of save_boot_params() weak function override.
Factor the save_boot_params() implementation into common cpu.c
code and provide accessors to read out both ROM API table address
and DT address from any place in the code instead.

Reviewed-by: Patrice Chotard <patrice.chotard@foss.st.com>
Reviewed-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Signed-off-by: Marek Vasut <marex@denx.de>
diff --git a/arch/arm/mach-stm32mp/include/mach/sys_proto.h b/arch/arm/mach-stm32mp/include/mach/sys_proto.h
index f19a70e..0d39b67 100644
--- a/arch/arm/mach-stm32mp/include/mach/sys_proto.h
+++ b/arch/arm/mach-stm32mp/include/mach/sys_proto.h
@@ -77,3 +77,6 @@
 
 /* helper function: read data from OTP */
 u32 get_otp(int index, int shift, int mask);
+
+uintptr_t get_stm32mp_rom_api_table(void);
+uintptr_t get_stm32mp_bl2_dtb(void);