cris: add missing declaration of kgdb_init() and breakpoint()

Fix:

  arch/cris/arch-v10/kernel/irq.c:239: error: implicit declaration of function 'kgdb_init'
  arch/cris/arch-v10/kernel/irq.c:240: error: implicit declaration of function 'breakpoint'

Declare these two functions.

Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: WANG Cong <xiyou.wangcong@gmail.com>
Cc: Mikael Starvik <starvik@axis.com>
Cc: Jesper Nilsson <jesper.nilsson@axis.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>