MIPS: Loongson64: Correct TLB type for Loongson-3 Classic

Huacai just informed me that some early Loongson-3A2000 had wrong
TLB type in Config0 register. That means we have to correct it via
PRID.

It looks like I shoudn't drop MIPS_CPU_FTLB flag in PRID case for
Loongson-3 Classic.

Fixes: da1bd297 ("MIPS: Loongson64: Probe CPU features via CPUCFG")
Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Reported-by: Huacai Chen <chenhc@lemote.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>