On mips, "struct user" bears no relation to the actual structure used by
PTRACE_GETREGS. The real structure is "struct pt_regs" which is declared
in asm/ptrace.h

Fixes golang/go#20338.

Change-Id: I604d27bd2b0a0903784380cbd3fa2fd9b9811fa5
Reviewed-on: https://go-review.googlesource.com/43431Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>