MIPS: syscall: Fix AUDIT value for O32 processes on MIPS64

On MIPS64, O32 processes set both TIF_32BIT_ADDR and
TIF_32BIT_REGS so the previous condition treated O32 applications
as N32 when evaluating seccomp filters. Fix the condition to check
both TIF_32BIT_{REGS, ADDR} for the N32 AUDIT flag.
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Patchwork: http://patchwork.linux-mips.org/patch/7480/
Cc: <stable@vger.kernel.org> # v3.15+
Signed-off-by: James Hogan <james.hogan@imgtec.com>

arch/mips/include/asm/syscall.h

@@ -131,10 +131,12 @@ static inline int syscall_get_arch(void)
 {
 	int arch = EM_MIPS;
 #ifdef CONFIG_64BIT
-	if (!test_thread_flag(TIF_32BIT_REGS))
+	if (!test_thread_flag(TIF_32BIT_REGS)) {
 		arch |= __AUDIT_ARCH_64BIT;
+		/* N32 sets only TIF_32BIT_ADDR */
 		if (test_thread_flag(TIF_32BIT_ADDR))
 			arch |= __AUDIT_ARCH_CONVENTION_MIPS64_N32;
+	}
 #endif
 #if defined(__LITTLE_ENDIAN)
 	arch |=  __AUDIT_ARCH_LE;