posix: Remove a non needed nil check in DiskInfo() (#8830)
posix: Remove a non needed nil check in DiskInfo() (#8830)

posix.DiskInfo() returns errFaultyDisk when posix is nil,
but there is no way that this would happen any time, therefore
removing un-needed code.
NitishT/minio,fwessels/minio,aead/minio,NitishT/minio,harshavardhana/minio,aead/minio,fwessels/minio,harshavardhana/minio,aead/minio,balamurugana/minio,minio/minio,NitishT/minio,krisis/minio,vadmeste/minio,fwessels/minio,harshavardhana/minio,minio/minio,harshavardhana/minio,NitishT/minio,donatello/minio,harshavardhana/minio,krisis/minio,harshavardhana/minio,harshavardhana/minio,fwessels/minio,aead/minio,aead/minio,aead/minio,donatello/minio,aead/minio,balamurugana/minio,harshavardhana/minio,aead/minio,vadmeste/minio