feat(st): disable authentication based on part_number

STM32MP15xA and STM32MP15xD chip part numbers don't
support the secure boot.
All functions linked to secure boot must not be used
and signed binaries are not allowed on such chip.

Signed-off-by: Lionel Debieve <lionel.debieve@st.com>
Change-Id: I5b85f322f5eb3b64415e1819bd00fb2c99f20695
diff --git a/plat/st/common/include/stm32mp_common.h b/plat/st/common/include/stm32mp_common.h
index cc06f5c..a13e9e5 100644
--- a/plat/st/common/include/stm32mp_common.h
+++ b/plat/st/common/include/stm32mp_common.h
@@ -21,6 +21,7 @@
 
 bool stm32mp_is_single_core(void);
 bool stm32mp_is_closed_device(void);
+bool stm32mp_is_auth_supported(void);
 
 /* Return the base address of the DDR controller */
 uintptr_t stm32mp_ddrctrl_base(void);