ring-buffer: Simplify if-if to if-else

Use if and else instead of if(A) and if (!A).

Link: https://lkml.kernel.org/r/20220426070628.167565-1-wanjiabing@vivo.com

Signed-off-by: Wan Jiabing <wanjiabing@vivo.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>