stubdom/vtpm: include stdio.h for declaration of printf

The function read_vtpmblk uses printf(3), but stdio.h is not included
in this file. This results in a warning from gcc-7:

vtpmblk.c: In function 'read_vtpmblk':
vtpmblk.c:322:7: warning: implicit declaration of function 'printf' [-Wimplicit-function-declaration]
       printf("Expected: ");
vtpmblk.c:322:7: warning: incompatible implicit declaration of built-in function 'printf'
vtpmblk.c:322:7: note: include '<stdio.h>' or provide a declaration of 'printf'

Signed-off-by: Olaf Hering <olaf@aepfle.de>
Acked-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Release-acked-by: Juergen Gross <jgross@suse.com>

stubdom/vtpm/vtpmblk.c

@@ -20,6 +20,7 @@
 #include <unistd.h>
 #include <errno.h>
 #include <fcntl.h>
+#include <stdio.h>
 
 /*Encryption key and block sizes */
 #define BLKSZ 16