Use crc32c for the verify_header checksum

It's the only hardware assisted crypto we have, and it's
widely available in any recent Intel CPU.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/verify.c b/verify.c
index d6abb98..f40d7e1 100644
--- a/verify.c
+++ b/verify.c
@@ -651,7 +651,7 @@
 	void *p = hdr;
 	uint32_t crc;
 
-	crc = crc32(p, sizeof(*hdr) - sizeof(hdr->crc32));
+	crc = crc32c(p, sizeof(*hdr) - sizeof(hdr->crc32));
 	if (crc == hdr->crc32)
 		return 1;
 
@@ -866,7 +866,7 @@
 	hdr->pad1 = 0;
 	hdr->rand_seed = io_u->rand_seed;
 	hdr->pad2 = 0;
-	hdr->crc32 = crc32(p, sizeof(*hdr) - sizeof(hdr->crc32));
+	hdr->crc32 = crc32c(p, sizeof(*hdr) - sizeof(hdr->crc32));
 
 	data_len = header_len - hdr_size(hdr);