powerpc/ps3: Re-align DTB in image

Change the PS3 linker script to align the DTB at 8 bytes,
the same alignment as that of the of the 'generic' powerpc
linker script.

Signed-off-by: Geoff Levand <geoff@infradead.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/245897ed65e402686a4b114ba618e935cb5c6506.1622822173.git.geoff@infradead.org