Including node_guid in InfiniBandDevice

[di3go-sona]

Hi, at my org we are using the infiniband collector in node_exporter .

For our case it's extremely useful to also export an unique identifier like node_guid that can be read from /sys/class/infiniband/<device>/node_guid

The exporter code heavily relies on the InfiniBandClass contained here, and that identifier is not collected

procfs/sysfs/class_infiniband.go

Lines 121 to 129 in a49c6d2

	// InfiniBandDevice contains info from files in /sys/class/infiniband for a
	// single InfiniBand device.
	type InfiniBandDevice struct {
	Name string
	BoardID string // /sys/class/infiniband/<Name>/board_id
	FirmwareVersion string // /sys/class/infiniband/<Name>/fw_ver
	HCAType string // /sys/class/infiniband/<Name>/hca_type
	Ports map[uint]InfiniBandPort
	}

Is there any design reason for this choic,e or can I just contribute a PR for that ?

[discordianfish]

Sounds reasonable, so a PR would be welcome.