Fix verify

The hole commit from yesterday (d3a173a9) had a bug, where
we would checksum too much.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/verify.c b/verify.c
index 6621966..0a504de 100644
--- a/verify.c
+++ b/verify.c
@@ -654,7 +654,7 @@
 	if (hdr->magic != FIO_HDR_MAGIC)
 		return 0;
 
-	crc = crc32c(p, sizeof(*hdr) - sizeof(hdr->crc32));
+	crc = crc32c(p, offsetof(struct verify_header, crc32));
 	if (crc == hdr->crc32)
 		return 1;
 
@@ -859,7 +859,7 @@
 	hdr->verify_type = td->o.verify;
 	hdr->len = header_len;
 	hdr->rand_seed = io_u->rand_seed;
-	hdr->crc32 = crc32c(p, sizeof(*hdr) - sizeof(hdr->crc32));
+	hdr->crc32 = crc32c(p, offsetof(struct verify_header, crc32));
 
 	data_len = header_len - hdr_size(hdr);