This patch adds padding bytes at the end of the last image in the
fip to be able to transfer by DMA the last image.

Change-Id: I8c6f07dee389cb3d1dc919936d9d52841d7e5723
Signed-off-by: Roberto Vargas <roberto.vargas@arm.com>
Signed-off-by: Dimitris Papastamos <dimitris.papastamos@arm.com>
Signed-off-by: David Cunado <david.cunado@arm.com>