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/drivers/st/clk/stm32mp1_clk.c b/drivers/st/clk/stm32mp1_clk.c
index f0bf363..b8457cb 100644
--- a/drivers/st/clk/stm32mp1_clk.c
+++ b/drivers/st/clk/stm32mp1_clk.c
@@ -1323,7 +1323,7 @@
 	int ret, len;
 	enum stm32mp1_pll_id i;
 	bool lse_css = false;
-	const uint32_t *pkcs_cell;
+	const fdt32_t *pkcs_cell;
 
 	/* Check status field to disable security */
 	if (!fdt_get_rcc_secure_status()) {
@@ -1529,7 +1529,7 @@
 		priv->pkcs_usb_value = 0;
 
 		for (j = 0; j < ((uint32_t)len / sizeof(uint32_t)); j++) {
-			uint32_t pkcs = (uint32_t)fdt32_to_cpu(pkcs_cell[j]);
+			uint32_t pkcs = fdt32_to_cpu(pkcs_cell[j]);
 
 			if (pkcs == (uint32_t)CLK_CKPER_DISABLED) {
 				ckper_disabled = true;