ring-buffer: Use sync sched protection on ring buffer resizing

There was a comment in the ring buffer code that says the calling
layers should prevent tracing or reading of the ring buffer while
resizing. I have discovered that the tracers do not honor this
arrangement.

This patch moves the disabling and synchronizing the ring buffer to
a higher layer during resizing. This guarantees that no writes
are occurring while the resize takes place.

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