layerscape: add ppa firmware package

This patch is to add PPA (The Primary Protected Application)
package and also enable it for all layerscape devices.
LSDK github provides ppa source code git tree, but it
only could be compiled with 64-bit toolchain. For 32-bit
devices, there was no method to use it.
https://github.com/qoriq-open-source/ppa-generic

This patch is to directly use a private ppa binary tree for
both 32-bit and 64-bit devices.

Signed-off-by: Yangbo Lu <yangbo.lu@nxp.com>