ARM: l2c: exynos: convert to generic l2c OF initialisation (and thereby fix it)

exynos was unconditionally calling the L2 cache initialisation from an
early_initcall.  This breaks multiplatform kernels.  Thankfully,
converting to generic l2c initialisation fixes this.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>