block: Allow t10-pi to be modular

Currently t10-pi can only be built into the block layer which via
crc-t10dif pulls in a whole chunk of the Crypto API.  In fact all
users of t10-pi work as modules and there is no reason for it to
always be built-in.

This patch adds a new hidden option for t10-pi that is selected
automatically based on BLK_DEV_INTEGRITY and whether the users
of t10-pi are built-in or not.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/t10-pi.c

@@ -7,6 +7,7 @@
 #include <linux/t10-pi.h>
 #include <linux/blkdev.h>
 #include <linux/crc-t10dif.h>
+#include <linux/module.h>
 #include <net/checksum.h>
 
 typedef __be16 (csum_fn) (void *, unsigned int);
@@ -280,3 +281,5 @@ const struct blk_integrity_profile t10_pi_type3_ip = {
 	.complete_fn		= t10_pi_type3_complete,
 };
 EXPORT_SYMBOL(t10_pi_type3_ip);
+
+MODULE_LICENSE("GPL");