[SCSI] scsi: add Kconfig dependency on NET

be2iscsi driver should #include linux/if_ether.h since it uses
sysfs_format_mac().

It should also depend on NET since it selects SCSI_ISCSI_ATTRS,
which depends on NET.

These changes fix a build error when CONFIG_NET is not enabled:
ERROR: "sysfs_format_mac" [drivers/scsi/be2iscsi/be2iscsi.ko] undefined!

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Acked-by: Jayamohan Kallickal <jayamohank@serverengines.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>