efi: new 'connectefi' command

[Renaud Métrich]

This set of patches fixes a memory leak in 'lsefi' command and
introduces a new 'connectefi pciroot|scsi' command which recursively
connects the corresponding EFI handles.
This is required on VMWare with efi.quickBoot enabled when chainloading
to grub on the harddisk from a network boot, otherwise none of the hard
disks are found (and sometimes the hard disk is found but not the
underneath partitions).

This is closely related to the following patchset:
[PATCH v3 1/2] search: fixed bug stopping iteration when --no-floppy is used
[PATCH v3 2/2] search: new --efidisk-only option on EFI systems