fb: cfb: avoid multiple strlen calls in draw_text

Added `len` to store the result of `strlen(str)` to avoid
multiple calls to `strlen` in the `for-loop`.

Signed-off-by: Pisit Sawangvonganan <[email protected]>

Author: ndrs-pst

subsys/fb/cfb.c

@@ -278,7 +278,9 @@ static int draw_text(const struct device *dev, const char *const str, int16_t x,
 	}
 
 	if ((fb->screen_info & SCREEN_INFO_MONO_VTILED)) {
-		for (size_t i = 0; i < strlen(str); i++) {
+		const size_t len = strlen(str);
+
+		for (size_t i = 0; i < len; i++) {
 			if ((x + fptr->width > fb->x_res) && wrap) {
 				x = 0U;
 				y += fptr->height;