x86: merge final linking scripts

x86: merge final linking scripts

While unrelated to the previous four patches, I realized that the two
scripts are nearly identical when coding those earlier patches, and
this patch depends on them in order to apply cleanly.

As an extra measure, it also adjusts the (unused) space freed at the
end of the per-CPU area to include all alignment space needed before
the first actual constituent of the .bss section (up to 7 pages on
x86-64).

Signed-off-by: Jan Beulich <jbeulich@novell.com>