MIPS: Fix syscall_get_nr for the syscall exit tracing.

Register 2 is alredy overwritten by the return value when
syscall_trace_leave() is called.

Signed-off-by: Lars Persson <larper@axis.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/9187/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

diff --cc arch/mips/include/asm/syscall.h
Simple merge

diff --cc arch/mips/include/asm/thread_info.h
Simple merge

diff --cc arch/mips/kernel/ptrace.c
Simple merge