arm: socfpga: cache: Enable PL310 L2 cache

arm: socfpga: cache: Enable PL310 L2 cache

Enable the PL310 L2 cache controller support for the SoCFPGA.
With the cache related issues resolved, this is safe to be done.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Chin Liang See <clsee@altera.com>
Cc: Dinh Nguyen <dinguyen@altera.com>
Cc: Albert Aribaud <albert.u.boot@aribaud.net>
Cc: Tom Rini <trini@ti.com>
Cc: Wolfgang Denk <wd@denx.de>
Cc: Pavel Machek <pavel@denx.de>
Acked-by: Pavel Machek <pavel@denx.de>