powerpc/powernv: powernv platform is not constrained by RMA

Remove incorrect comment about real mode address restrictions on
powernv (bare metal), and unnecessary clamping to ppc64_rma_size.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
1 file changed