MIPS: ioctl.h: Cleanup.

 o Rewrite to use <asm-generic/ioctl.h>.  Cuts down the file from 40 to
   16 lines.
 o Delete _IOC_VOID, _IOC_OUT, _IOC_IN and _IOC_INOUT.  They were added
   for 2.1.14 but I was not able to find any user - not even historical
   ones.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>