ARM platforms: Reintroduce coherent memory for BL1 and BL2

The patch d323af9e removed the support for coherent memory in BL1 and
BL2 for ARM platforms. But the CryptoCell SBROM  integration depends
on use of coherent buffers for passing data from the AP CPU to the
CryptoCell. Hence this patch reintroduces support for coherent
memory in BL1 and BL2 if ARM_CRYPTOCELL_INTEG=1.

Change-Id: I011482dda7f7a3ec9e3e79bfb3f4fa03796f7e02
Signed-Off-by: Soby Mathew <soby.mathew@arm.com>