ARM: l2c: AM43x: add L2 cache support

Add support for L2 cache controller (PL310) on AM437x SoC.

Signed-off-by: Sekhar Nori <nsekhar@ti.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>