mk_socket: Added a variable that accepts return value for read() in tcp_autocorking function

Added a variable to accept the return value of read() function in mk_socket_tcp_autocorking ().
Motivation: It removes the following warning that arises during 'make'

---------------  WARNING  --------------------
mk_socket.c: In function ‘mk_socket_tcp_autocorking’:
mk_socket.c:265:9: warning: ignoring return value of ‘read’, declared with attribute warn_unused_result [-Wunused-result]
---------------  WARNING  --------------------