Fix %lld or %llx printf format use

Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
diff --git a/nbd.c b/nbd.c
index 337eeba..a9f295f 100644
--- a/nbd.c
+++ b/nbd.c
@@ -353,8 +353,7 @@
 		return -1;
 	}
 
-	TRACE("Setting size to %llu block(s)",
-	      (unsigned long long)(size / blocksize));
+        TRACE("Setting size to %zd block(s)", (size_t)(size / blocksize));
 
 	if (ioctl(fd, NBD_SET_SIZE_BLOCKS, size / blocksize) == -1) {
 		int serrno = errno;