rxrpc: Fix handling of enums-to-string translation in tracing

Fix the way enum values are translated into strings in AF_RXRPC
tracepoints.  The problem with just doing a lookup in a normal flat array
of strings or chars is that external tracing infrastructure can't find it.
Rather, TRACE_DEFINE_ENUM must be used.

Also sort the enums and string tables to make it easier to keep them in
order so that a future patch to __print_symbolic() can be optimised to try
a direct lookup into the table first before iterating over it.

A couple of _proto() macro calls are removed because they refered to tables
that got moved to the tracing infrastructure.  The relevant data can be
found by way of tracing.

Signed-off-by: David Howells <dhowells@redhat.com>