style: add braces around if/while statements

Per guidelines, all statements should have braces around them. We do not
have a CI check for this, so a few went in unnoticed.

Signed-off-by: Anas Nashif <anas.nashif@intel.com>
diff --git a/lib/libc/minimal/source/string/string.c b/lib/libc/minimal/source/string/string.c
index a974227..8fcd271 100644
--- a/lib/libc/minimal/source/string/string.c
+++ b/lib/libc/minimal/source/string/string.c
@@ -68,8 +68,9 @@
 {
 	char tmp = (char) c;
 
-	while ((*s != tmp) && (*s != '\0'))
+	while ((*s != tmp) && (*s != '\0')) {
 		s++;
+	}
 
 	return (*s == tmp) ? (char *) s : NULL;
 }
@@ -180,8 +181,9 @@
 	const char *c1 = m1;
 	const char *c2 = m2;
 
-	if (!n)
+	if (!n) {
 		return 0;
+	}
 
 	while ((--n > 0) && (*c1 == *c2)) {
 		c1++;
diff --git a/lib/libc/minimal/source/string/strstr.c b/lib/libc/minimal/source/string/strstr.c
index 7334893..7de678f 100644
--- a/lib/libc/minimal/source/string/strstr.c
+++ b/lib/libc/minimal/source/string/strstr.c
@@ -51,8 +51,9 @@
 		do {
 			do {
 				sc = *s++;
-				if (sc == 0)
-				return NULL;
+				if (sc == 0) {
+					return NULL;
+				}
 			} while (sc != c);
 		} while (strncmp(s, find, len) != 0);
 	s--;