geometry: Add boot_lchs_find_*() utility functions

geometry: Add boot_lchs_find_*() utility functions

Adding the following utility functions:

    * boot_lchs_find_pci_device
    * boot_lchs_find_scsi_device
    * boot_lchs_find_ata_device

These will be used to apply LCHS values received through fw_cfg.

Reviewed-by: Karl Heubaum <karl.heubaum@oracle.com>
Reviewed-by: Arbel Moshe <arbel.moshe@oracle.com>
Signed-off-by: Sam Eiderman <shmuel.eiderman@oracle.com>
Message-Id: <20190612093704.47175-4-shmuel.eiderman@oracle.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>