MIPS: Ensure Config5.UFE is clear on boot

As is done for UFR, ensure that userland cannot directly manipulate the
mode by clearing the UFE bit during boot.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/7677/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/kernel/cpu-probe.c

@@ -461,7 +461,7 @@ static inline unsigned int decode_config5(struct cpuinfo_mips *c)
 	unsigned int config5;
 
 	config5 = read_c0_config5();
-	config5 &= ~MIPS_CONF5_UFR;
+	config5 &= ~(MIPS_CONF5_UFR | MIPS_CONF5_UFE);
 	write_c0_config5(config5);
 
 	if (config5 & MIPS_CONF5_EVA)