ARM: OMAP5 / DRA7: Setup L2 Aux Control Register with recommended configuration

Update to existing recommendation for L2ACTLR configuration to prevent
system instability and optimize performance.

These apply to both OMAP5 and DRA7.

Reported-by: Vivek Chengalvala <vchengalvala@ti.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>