MIPS: Fix MIPS I ISA /proc/cpuinfo reporting

Correct a commit 515a6393db ("MIPS: kernel: proc: Add MIPS R6 support
to /proc/cpuinfo") regression that caused MIPS I systems to show no ISA
levels supported in /proc/cpuinfo, e.g.:

system type		: Digital DECstation 2100/3100
machine			: Unknown
processor		: 0
cpu model		: R3000 V2.0  FPU V2.0
BogoMIPS		: 10.69
wait instruction	: no
microsecond timers	: no
tlb_entries		: 64
extra interrupt vector	: no
hardware watchpoint	: no
isa			:
ASEs implemented	:
shadow register sets	: 1
kscratch registers	: 0
package			: 0
core			: 0
VCED exceptions		: not available
VCEI exceptions		: not available

and similarly exclude `mips1' from the ISA list for any processors below
MIPSr1.  This is because the condition to show `mips1' on has been made
`cpu_has_mips_r1' rather than newly-introduced `cpu_has_mips_1'.  Use
the correct condition then.

Fixes: 515a6393db ("MIPS: kernel: proc: Add MIPS R6 support to /proc/cpuinfo")
Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Reviewed-by: James Hogan <james.hogan@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: stable@vger.kernel.org # 3.19+
Patchwork: https://patchwork.linux-mips.org/patch/16758/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/kernel/proc.c

@@ -83,7 +83,7 @@ static int show_cpuinfo(struct seq_file *m, void *v)
 	}
 
 	seq_printf(m, "isa\t\t\t:"); 
-	if (cpu_has_mips_r1)
+	if (cpu_has_mips_1)
 		seq_printf(m, " mips1");
 	if (cpu_has_mips_2)
 		seq_printf(m, "%s", " mips2");