x86: reorder .data and .init when linking

x86: reorder .data and .init when linking

In preparation for using superpage mappings, .data and .bss will both want to
be mapped as read-write.  By making them adjacent, they can share the same
superpage and will not require superpage alignment between themselves.

While making this change, fix a latent alignment bug whereby the alignment for
.bss.stack_aligned was in .init.  __init_end only needs page alignment (due to
being reclaimed after boot), while .bss.stack_aligned really does needs
STACK_SIZE alignment.

Suggested-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>