tcp: Export to userspace the TCP state names for the trace events

The TCP trace events (specifically tcp_set_state), maps emums to symbol
names via __print_symbolic(). But this only works for reading trace events
from the tracefs trace files. If perf or trace-cmd were to record these
events, the event format file does not convert the enum names into numbers,
and you get something like:

__print_symbolic(REC->oldstate,
    { TCP_ESTABLISHED, "TCP_ESTABLISHED" },
    { TCP_SYN_SENT, "TCP_SYN_SENT" },
    { TCP_SYN_RECV, "TCP_SYN_RECV" },
    { TCP_FIN_WAIT1, "TCP_FIN_WAIT1" },
    { TCP_FIN_WAIT2, "TCP_FIN_WAIT2" },
    { TCP_TIME_WAIT, "TCP_TIME_WAIT" },
    { TCP_CLOSE, "TCP_CLOSE" },
    { TCP_CLOSE_WAIT, "TCP_CLOSE_WAIT" },
    { TCP_LAST_ACK, "TCP_LAST_ACK" },
    { TCP_LISTEN, "TCP_LISTEN" },
    { TCP_CLOSING, "TCP_CLOSING" },
    { TCP_NEW_SYN_RECV, "TCP_NEW_SYN_RECV" })

Where trace-cmd and perf do not know the values of those enums.

Use the TRACE_DEFINE_ENUM() macros that will have the trace events convert
the enum strings into their values at system boot. This will allow perf and
trace-cmd to see actual numbers and not enums:

__print_symbolic(REC->oldstate,
    { 1, "TCP_ESTABLISHED" },
    { 2, "TCP_SYN_SENT" },
    { 3, "TCP_SYN_RECV" },
    { 4, "TCP_FIN_WAIT1" },
    { 5, "TCP_FIN_WAIT2" },
    { 6, "TCP_TIME_WAIT" },
    { 7, "TCP_CLOSE" },
    { 8, "TCP_CLOSE_WAIT" },
    { 9, "TCP_LAST_ACK" },
    { 10, "TCP_LISTEN" },
    { 11, "TCP_CLOSING" },
    { 12, "TCP_NEW_SYN_RECV" })

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Acked-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>