Add missing includes.

Change-Id: I91730363386dae6ecb2193ec8f50ba9f8fc0ad60
diff --git a/modules/nfc/nfc_pn544_example.c b/modules/nfc/nfc_pn544_example.c
index 54c9c56..71bfd6b 100644
--- a/modules/nfc/nfc_pn544_example.c
+++ b/modules/nfc/nfc_pn544_example.c
@@ -14,6 +14,7 @@
  * limitations under the License.
  */
 #include <errno.h>
+#include <malloc.h>
 #include <string.h>
 
 #include <hardware/hardware.h>