fix(st): explicitly check operators precedence

This corrects the MISRA violation C2012-12.1:
The precedence of operators within expressions should be made explicit.
This is done either by adding parentheses, or by creating dedicated
variables to ease readability.

Signed-off-by: Yann Gautier <yann.gautier@st.com>
Change-Id: I5e3f191ee38eca7ef634bd7542e615ab625271f6
diff --git a/plat/st/common/stm32mp_dt.c b/plat/st/common/stm32mp_dt.c
index c9efeb5..5681fa6 100644
--- a/plat/st/common/stm32mp_dt.c
+++ b/plat/st/common/stm32mp_dt.c
@@ -416,7 +416,7 @@
 
 		/* Get the last defined gpio line (offset + nb of pins) */
 		pin_count = fdt32_to_cpu(*(cuint + 1)) + fdt32_to_cpu(*(cuint + 3));
-		for (i = 0; i < len / 4; i++) {
+		for (i = 0; i < (len / 4); i++) {
 			pin_count = MAX(pin_count, (int)(fdt32_to_cpu(*(cuint + 1)) +
 							 fdt32_to_cpu(*(cuint + 3))));
 			cuint += 4;