Remove MIPS version of waitid.c.

Since glibc is no longer built with -Winline, a special MIPS version
of waitid.c to disable -Winline is no longer needed, and this patch
removes it.  Tested that glibc does indeed build with the patch
applied.

	* sysdeps/unix/sysv/linux/mips/mips32/waitid.c: Remove file.