cxd56xx/cxd56_emmc.c: Fix compile warning

Add necessary include header named debug.h for using ferr and
finfo.

arch/arm/src/cxd56xx/cxd56_emmc.c

@@ -28,6 +28,7 @@
 #include <stdint.h>
 #include <string.h>
 #include <assert.h>
+#include <debug.h>
 #include <errno.h>
 
 #include <nuttx/arch.h>