ring-buffer: move code around to remove some branches

This is a bit of micro-optimizations. But since the ring buffer is used
in tracing every function call, it is an extreme hot path. Every nanosecond
counts.

This change shows over 5% improvement in the ring-buffer-benchmark.

[ Impact: more efficient code ]

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

diff --cc kernel/trace/ring_buffer.c
Simple merge