cris build fixes: irq fixes

- New file include/asm-cris/irq_regs.h.
- Change handling of registers for do_IRQ.
- Add GENERIC_HARDIRQS to Kconfig.

Signed-off-by: Jesper Nilsson <jesper.nilsson@axis.com>
Acked-by: Mikael Starvik <starvik@axis.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>