drivers: fix up various ->llseek() implementations

Fix up a few ->llseek() implementations that won't deal with SEEK_HOLE/SEEK_DATA
properly.  Make them future proof so that if we ever add new options they will
return -EINVAL.  Thanks,

Signed-off-by: Josef Bacik <josef@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

drivers/char/nvram.c

@@ -224,6 +224,8 @@ static loff_t nvram_llseek(struct file *file, loff_t offset, int origin)
 	case 2:
 		offset += NVRAM_BYTES;
 		break;
+	default:
+		return -EINVAL;
 	}
 
 	return (offset >= 0) ? (file->f_pos = offset) : -EINVAL;