fix(st-regulator): use Boolean type for tests

This corrects MISRA C2012-14.4
The controlling expression of an if statement and the controlling
expression of an iteration-statement shall have essentially Boolean type.

Signed-off-by: Yann Gautier <yann.gautier@st.com>
Change-Id: Iacc58349cc3ab558fb4ffe0605a623e84e21e035
diff --git a/drivers/st/regulator/regulator_core.c b/drivers/st/regulator/regulator_core.c
index f15e22a..2a5d0f7 100644
--- a/drivers/st/regulator/regulator_core.c
+++ b/drivers/st/regulator/regulator_core.c
@@ -158,7 +158,7 @@
 
 	assert(rdev != NULL);
 
-	if (rdev->flags & REGUL_ALWAYS_ON) {
+	if ((rdev->flags & REGUL_ALWAYS_ON) != 0U) {
 		return 0;
 	}