powerpc/44x/fsp2: Add fsp2 headers

Add cmu, plbX, l2, ddr3/4, crcs register definitions.
Add mfcmu, mtcmu functions for indirect access to cmu.
Add mtl2, mfl2 same for l2 cache core reg set.

Signed-off-by: Ivan Mikhaylov <ivan@de.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>