ARM: 5845/1: l2x0: check whether l2x0 already enabled

If running in non-secure mode accessing
some registers of l2x0 will fault. So
check if l2x0 is already enabled, if so
do not access those secure registers.

Signed-off-by: srinidhi kasagar <srinidhi.kasagar@stericsson.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>