mips: remove the broken BINFMT_IRIX code

The BINFMT_IRIX code:
- has been marked as BROKEN for more than two years years and
- is still marked as BROKEN.

Code that has been marked as BROKEN for such a long time seem to be unlikely to be revived in the forseeable future.

But if anyone wants to ever revive this driver, the code is still present in the older kernel releases.

---

Due to it's size, the patch is attached compressed.

 arch/mips/Kconfig              |    4 
 arch/mips/kernel/Makefile      |    4 
 arch/mips/kernel/irix5sys.S    | 1041 ----------------
 arch/mips/kernel/irixelf.c     | 1332 --------------------
 arch/mips/kernel/irixinv.c     |   78 -
 arch/mips/kernel/irixioctl.c   |  251 ---
 arch/mips/kernel/irixsig.c     |  880 -------------
 arch/mips/kernel/process.c     |    7 
 arch/mips/kernel/scall32-o32.S |   18 
 arch/mips/kernel/sysirix.c     | 2140 ---------------------------------
 include/asm-mips/signal.h      |    3 
 11 files changed, 5758 deletions(-)