ARM: mm: Remove unnecessary CMO in Cortex A15 startup

Cortex-A15 flush L2 cache after reset, there is no need to do this
in software, if L2 is already invalidated in bootloader and
cache is disabled. For secondary startup, there is no reason to
flush L2 as well.

This change assumes the setup code is always entered as the result
of CPU reset.

Signed-off-by: Bo Yan <byan@nvidia.com>
Reviewed-by: Mrutyunjay Sawant <msawant@nvidia.com>
Tested-by: Mrutyunjay Sawant <msawant@nvidia.com>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
Signed-off-by: Chet Kener <Cl3Kener@gmail.com>

Change-Id: Iaca65c6df06282442824052d93cb0540d449a918