tracing: Move buffer in trace_seq to end of struct

tracing: Move buffer in trace_seq to end of struct

TRACE_SEQ_BUFFER_SIZE is dependent on the architecture for its size. on 64-bit
systems, it is 8148 bytes. forced 8-byte alignment in size_t and seq_buf means
that trace_seq is 8200 bytes on 64-bit systems. moving the buffer to the end
of the struct fixes the issue. there shouldn't be any side effects, i.e.
pointer arithmetic on trace_seq

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://lore.kernel.org/20250821053917.23301-1-git@elijahs.space
Signed-off-by: Elijah Wright <git@elijahs.space>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>