ARM: dts: exynos: add prefetch properties for L2C-310 cache

Add the devicetree properties to enable instruction and data prefetch
on exynos4210 and exynos4412 which use the L2C-310 cache.  No other
Exynos chip appears to be using this L2 cache hardware.

This follows the default bits being set in the l2c_aux_val register
for the Exynos platform, which can now be cleared as a result.

Signed-off-by: Guillaume Tucker <guillaume.tucker@collabora.com>
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>