ecryptfs: Drop TODO comment in ecryptfs_derive_iv

Remove the TODO from 2006. eCryptfs is generally not receiving new
features and changing the IV derivation is only likely to happen to
address security concerns in the future.

Signed-off-by: Thorsten Blum <thorsten.blum@linux.dev>
[tyhicks: Add the reasoning to the commit message]
Signed-off-by: Tyler Hicks <code@tyhicks.com>

Author: toblux

fs/ecryptfs/crypto.c

@@ -89,10 +89,6 @@ void ecryptfs_derive_iv(char *iv, struct ecryptfs_crypt_stat *crypt_stat,
 		ecryptfs_printk(KERN_DEBUG, "root iv:\n");
 		ecryptfs_dump_hex(crypt_stat->root_iv, crypt_stat->iv_bytes);
 	}
-	/* TODO: It is probably secure to just cast the least
-	 * significant bits of the root IV into an unsigned long and
-	 * add the offset to that rather than go through all this
-	 * hashing business. -Halcrow */
 	memcpy(src, crypt_stat->root_iv, crypt_stat->iv_bytes);
 	memset((src + crypt_stat->iv_bytes), 0, 16);
 	snprintf((src + crypt_stat->iv_bytes), 16, "%lld", offset);