hw/i386/pc: rename functions shared with non-PC machines

hw/i386/pc: rename functions shared with non-PC machines

The following functions are named *pc* but are not PC-machine specific
but generic to the X86 architecture, rename them:

  load_linux                 -> x86_load_linux
  pc_new_cpu                 -> x86_new_cpu
  pc_cpus_init               -> x86_cpus_init
  pc_cpu_index_to_props      -> x86_cpu_index_to_props
  pc_get_default_cpu_node_id -> x86_get_default_cpu_node_id
  pc_possible_cpu_arch_ids   -> x86_possible_cpu_arch_ids
  old_pc_system_rom_init     -> x86_system_rom_init

Signed-off-by: Sergio Lopez <slp@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>