stm32mp1: correct some static analysis tools issues

These issues wer found by sparse:

drivers/st/clk/stm32mp1_clk.c:1524:19:
 warning: incorrect type in assignment (different base types)
    expected restricted fdt32_t const [usertype] *pkcs_cell
    got unsigned int const [usertype] *

plat/st/stm32mp1/plat_image_load.c:13:6:
 warning: symbol 'plat_flush_next_bl_params' was not declared.
 Should it be static?
plat/st/stm32mp1/plat_image_load.c:21:16:
 warning: symbol 'plat_get_bl_image_load_info' was not declared.
 Should it be static?
plat/st/stm32mp1/plat_image_load.c:29:13:
 warning: symbol 'plat_get_next_bl_params' was not declared.
 Should it be static?

plat/st/stm32mp1/bl2_io_storage.c:40:10:
 warning: symbol 'block_buffer' was not declared. Should it be static?

Signed-off-by: Yann Gautier <yann.gautier@st.com>
diff --git a/include/drivers/st/stm32mp1_clkfunc.h b/include/drivers/st/stm32mp1_clkfunc.h
index b11ccf8..2467af9 100644
--- a/include/drivers/st/stm32mp1_clkfunc.h
+++ b/include/drivers/st/stm32mp1_clkfunc.h
@@ -7,6 +7,7 @@
 #ifndef STM32MP1_CLKFUNC_H
 #define STM32MP1_CLKFUNC_H
 
+#include <libfdt.h>
 #include <stdbool.h>
 
 enum stm32mp_osc_id {
@@ -33,7 +34,7 @@
 int fdt_rcc_read_uint32_array(const char *prop_name,
 			      uint32_t *array, uint32_t count);
 int fdt_rcc_subnode_offset(const char *name);
-const uint32_t *fdt_rcc_read_prop(const char *prop_name, int *lenp);
+const fdt32_t *fdt_rcc_read_prop(const char *prop_name, int *lenp);
 bool fdt_get_rcc_secure_status(void);
 
 uintptr_t fdt_get_stgen_base(void);