arm-bsp: remove cortex-a tune files

Cortex-a tune files have been accepted into openembedded-core.  So,
those should be used in place of these.  Removing these to prevent any
issues.

Change-Id: Ifca1557a88e50ce6947524222ba7f852fd9a282c
Signed-off-by: Jon Mason <jon.mason@arm.com>