x86: Clean up the loadsegment() macro

Make it readable in the source too, not just in the assembly output.
No change in functionality.

Cc: Brian Gerst <brgerst@gmail.com>
LKML-Reference: <1259176706-5908-1-git-send-email-brgerst@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>