fdts: a5ds: cleanup enable-method in devicetree
fdts: a5ds: cleanup enable-method in devicetree

Same enable method is used by all the four cores. So,
make it globally for all the cores instead of adding
it to individual level.

Change-Id: I9b5728b0e0545c9e27160ea586009d929eb78cad
Signed-off-by: Vishnu Banavath <03aa44955b4cdec5390ffe720a94542b904bd4bb@arm.com>

achingupta/arm-trusted-firmware,achingupta/arm-trusted-firmware