Fix MIPS n32 pr_sigpend, pr_sighold, pr_flag type (bug 23656).

As discussed at
<https://sourceware.org/ml/libc-alpha/2018-09/msg00191.html> and
followup discussions, the MIPS n32 definitions of pr_sigpend and
pr_sighold in struct elf_prstatus, and pr_flag in struct elf_prpsinfo,
are wrong to use unsigned long long int; actual n32 core dumps use a
32-bit type there, so userspace unsigned long int is correct for all
MIPS ABIs.  This patch removes the conditionals (also thereby aligning
the structures with other architectures and so facilitating future
unification of different versions of this header).

Tested with build-many-glibcs.py for its MIPS configurations.

	[BZ #23656]
	* sysdeps/unix/sysv/linux/mips/sys/procfs.h (struct elf_prstatus):
	Remove [_MIPS_SIM = _ABIN32] conditional case.
	(struct elf_prpsinfo): Likewise.