oprofile: adding cpu buffer r/w access functions

This is in preparation for changes in the cpu buffer implementation.

Signed-off-by: Robert Richter <robert.richter@amd.com>

diff --cc drivers/oprofile/buffer_sync.c
Simple merge

diff --cc drivers/oprofile/cpu_buffer.c
Simple merge

diff --cc drivers/oprofile/cpu_buffer.h
Simple merge