fscrypt: rename fscrypt_do_page_crypto() to fscrypt_crypt_block()

fscrypt_do_page_crypto() only does a single encryption or decryption
operation, with a single logical block number (single IV).  So it
actually operates on a filesystem block, not a "page" per se.  To
reflect this, rename it to fscrypt_crypt_block().

Reviewed-by: Chandan Rajendra <chandan@linux.ibm.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>

fs/crypto/bio.c

@@ -83,9 +83,9 @@ int fscrypt_zeroout_range(const struct inode *inode, pgoff_t lblk,
 		return -ENOMEM;
 
 	while (len--) {
-		err = fscrypt_do_page_crypto(inode, FS_ENCRYPT, lblk,
-					     ZERO_PAGE(0), ciphertext_page,
-					     PAGE_SIZE, 0, GFP_NOFS);
+		err = fscrypt_crypt_block(inode, FS_ENCRYPT, lblk,
+					  ZERO_PAGE(0), ciphertext_page,
+					  PAGE_SIZE, 0, GFP_NOFS);
 		if (err)
 			goto errout;