x86: beautify vmlinux_64.lds.S

Beautify vmlinux_64.lds.S:

 - Use tabs for indent
 - Located curly braces like in C code
 - Rearranged a few comments

There is no functional changes in this patch

The beautification is done to prepare a unification
of the _32 and the _64 variants of the linker scripts.

[ Impact: cleanup ]
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Tim Abbott <tabbott@MIT.EDU>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
LKML-Reference: <20090426210742.GA3464@uranus.ravnborg.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>