powerpc: e6500: Lock/unlock 1 cache instead of L1 as init_ram

For E6500 cores, L2 cache has been used as init_ram. L1 cache is a
write through cache on E6500.If lines are not locked in both L1 and
L2 caches, crashes are observed during secure boot. This patch locks/
unlocks both L1 and L2 cache to prevent the crash.

Signed-off-by: Ruchika Gupta <ruchika.gupta@nxp.com>
Reviewed-by: York Sun <york.sun@nxp.com>