LoongArch: Fix wrong fpu version

According to the configuration information accessible by the CPUCFG
instruction in LoongArch Reference Manual [1], FP_ver is stored in
bit [5: 3] of CPUCFG2, the current code to get fpu version is wrong,
use CPUCFG2_FPVERS to fix it.

[1] https://loongson.github.io/LoongArch-Documentation/LoongArch-Vol1-EN.html

Fixes: 628c3bb4 ("LoongArch: Add boot and setup routines")
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

arch/loongarch/kernel/cpu-probe.c

@@ -263,7 +263,7 @@ void cpu_probe(void)
 
 	c->cputype	= CPU_UNKNOWN;
 	c->processor_id = read_cpucfg(LOONGARCH_CPUCFG0);
-	c->fpu_vers	= (read_cpucfg(LOONGARCH_CPUCFG2) >> 3) & 0x3;
+	c->fpu_vers     = (read_cpucfg(LOONGARCH_CPUCFG2) & CPUCFG2_FPVERS) >> 3;
 
 	c->fpu_csr0	= FPU_CSR_RN;
 	c->fpu_mask	= FPU_CSR_RSVD;