Moves the source code for ring buffers to the 'misc' area, since
it isn't really a central component of the kernel. (This also
aligns the ring buffer source code with its include file, which
is already under 'include/misc'.)
Change-Id: I765a383a05f51fa67d154446f412496e689f9702
Signed-off-by: Allan Stephens <allan.stephens@windriver.com>