stm32: Correct positioning of declaration

The current code gives a warning:

arch/arm/mach-stm32/stm32f7/soc.c: In function 'arch_cpu_init':
arch/arm/mach-stm32/stm32f7/soc.c:38:2: error: 'for' loop initial
    declarations are only allowed in C99 or C11 mode
  for (int i = 0; i < ARRAY_SIZE(stm32_region_config); i++)
  ^
arch/arm/mach-stm32/stm32f7/soc.c:38:2: note: use option -std=c99,
    -std=gnu99, -std=c11 or -std=gnu11 to compile your code

Fix it by moving the declaration to the top of the function.

Signed-off-by: Simon Glass <sjg@chromium.org>
Series-cc trini

arch/arm/mach-stm32/stm32f7/soc.c

@@ -17,6 +17,8 @@ u32 get_cpu_rev(void)
 
 int arch_cpu_init(void)
 {
+	int i;
+
 	struct mpu_region_config stm32_region_config[] = {
 		{ 0x00000000, REGION_0, XN_DIS, PRIV_RW_USR_RW,
 		O_I_WB_RD_WR_ALLOC, REGION_4GB },
@@ -35,7 +37,7 @@ int arch_cpu_init(void)
 	};
 
 	disable_mpu();
-	for (int i = 0; i < ARRAY_SIZE(stm32_region_config); i++)
+	for (i = 0; i < ARRAY_SIZE(stm32_region_config); i++)
 		mpu_config(&stm32_region_config[i]);
 	enable_mpu();