cpu: Add the matching rule "Model Name" when parsing cpuinfo

This is to fix the error of running TestCpuInfo on Linux/long64. In loong64
/proc/cpuinfo, the model name is capitalize the first letter

Reference:
  https://github.com/torvalds/linux/blob/master/arch/loongarch/kernel/proc.c

Signed-off-by: Guoqi Chen <chenguoqi@loongson.cn>

cpu/cpu_linux.go

@@ -253,7 +253,7 @@ func InfoWithContext(ctx context.Context) ([]InfoStat, error) {
 					}
 				}
 			}
-		case "model name", "cpu":
+		case "Model Name", "model name", "cpu":
 			c.ModelName = value
 			if strings.Contains(value, "POWER8") ||
 				strings.Contains(value, "POWER7") {