Fix the following W=1 kernel warnings:
arch/x86/xen/setup.c:725: warning: expecting prototype for
machine_specific_memory_setup(). Prototype was for xen_memory_setup()
instead.
Reported-by: Abaci Robot <abaci@xxxxxxxxxxxxxxxxx>
Signed-off-by: Jiapeng Chong <jiapeng.chong@xxxxxxxxxxxxxxxxx>