Fix

WARNING: vmlinux.o(.data+0x99): Section mismatch: reference to .init.text:xen_start_kernel (between 'startup_xen' and 'boot_gdt_descr')
Signed-off-by: NAndi Kleen <ak@suse.de>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>