[nrf noup] settings: Increase max length for settings

Increase the maximum length for settings to accommodate the new
fields added in `wifi_credentials_header`.

Signed-off-by: Ravi Dondaputi <[email protected]>

Author: rado17

include/zephyr/settings/settings.h

@@ -36,7 +36,7 @@ extern "C" {
 
 #define SETTINGS_MAX_DIR_DEPTH	8	/* max depth of settings tree */
 #define SETTINGS_MAX_NAME_LEN	(8 * SETTINGS_MAX_DIR_DEPTH)
-#define SETTINGS_MAX_VAL_LEN	256
+#define SETTINGS_MAX_VAL_LEN	512
 #define SETTINGS_NAME_SEPARATOR	'/'
 #define SETTINGS_NAME_END '='