doc: Fix documentation of EVP_EncryptUpdate().

The documentation was off by one for the length this function could return.
Reviewed-by: NTomas Mraz <tmraz@fedoraproject.org>
(Merged from https://github.com/openssl/openssl/pull/12435)

doc/man3/EVP_EncryptInit.pod

@@ -210,10 +210,15 @@ specified.
 EVP_EncryptUpdate() encrypts B<inl> bytes from the buffer B<in> and
 writes the encrypted version to B<out>. This function can be called
 multiple times to encrypt successive blocks of data. The amount
-of data written depends on the block alignment of the encrypted data:
-as a result the amount of data written may be anything from zero bytes
-to (inl + cipher_block_size - 1) so B<out> should contain sufficient
-room. The actual number of bytes written is placed in B<outl>. It also
+of data written depends on the block alignment of the encrypted data.
+For most ciphers and modes, the amount of data written can be anything
+from zero bytes to (inl + cipher_block_size - 1) bytes.
+For wrap cipher modes, the amount of data written can be anything
+from zero bytes to (inl + cipher_block_size) bytes.
+For stream ciphers, the amount of data written can be anything from zero
+bytes to inl bytes.
+Thus, B<out> should contain sufficient room for the operation being performed.
+The actual number of bytes written is placed in B<outl>. It also
 checks if B<in> and B<out> are partially overlapping, and if they are
 0 is returned to indicate failure.