[MIPS] Enable support for the userlocal hardware register

Which will cut down the cost of RDHWR $29 which is used to obtain the
TLS pointer and so far being emulated in software down to a single cycle
operation.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/kernel/traps.c

@@ -1341,7 +1341,14 @@ void __init per_cpu_trap_init(void)
 		set_c0_status(ST0_MX);
 
 #ifdef CONFIG_CPU_MIPSR2
-	write_c0_hwrena (0x0000000f); /* Allow rdhwr to all registers */
+	if (cpu_has_mips_r2) {
+		unsigned int enable = 0x0000000f;
+
+		if (cpu_has_userlocal)
+			enable |= (1 << 29);
+
+		write_c0_hwrena(enable);
+	}
 #endif
 
 #ifdef CONFIG_MIPS_MT_SMTC