cris/kgdb: Kill forward declarations for static functions

Move some functions around and kill forward declarations for static
functions. This fixes:

arch/cris/arch-v10/kernel/kgdb.c:255:13: warning: 'copy_registers_from_stack' declared 'static' but never defined [-Wunused-function]
arch/cris/arch-v10/kernel/kgdb.c:259:13: warning: 'copy_registers_to_stack' declared 'static' but never defined [-Wunused-function]
arch/cris/arch-v10/kernel/kgdb.c:267:12: warning: 'write_stack_register' declared 'static' but never defined [-Wunused-function]
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>