Basically, in the portability layer, it is checked if the socket is
NON-block, and if not, then even the EAGAIN and EWOULDBLOCK errors are
diverted to a RECV error. This causes a problem for sockets with
receive timeouts set. When such a timeout is set, the condition for
NON_BLOCK isn't met and hence a hard error is returned.
Searching for EAGAIN and EWOULDBLOCK in lwip returns only 3 results
(accept, recvfrom, close) and all of them look to be genuine cases for
EWOULDBLOCK. So removing this check to make receive timeout with TLS
work.
