tune-cortexa*.inc: fix tunings for cortex a5, a7, a8, a9, a15 machines.

Using CORTEX_ID variable reference in the tuning overrides did not work.
This reverts those changes, and adds a tuning file for the cortex-a5.

Revert "tune-cortexa5.inc: Add tune file for cortex-a5"
Revert "tune-cortexa.inc: create a common include for cortex-a armv7a tuning"

Signed-off-by: Andy Voltz <andy.voltz@timesys.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>