x86, realmode: Relocator for realmode code

Implements relocator for real mode code that is called
as part of setup_arch(). Processes segment relocations
and linear relocations. Real-mode code is relocated to
a free hole below 1 MB.

Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@intel.com>
Link: http://lkml.kernel.org/r/1336501366-28617-4-git-send-email-jarkko.sakkinen@intel.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>