Some ECKD bootmap code was using structs designed for SCSI.
Even though this works, it confuses readability. Add a new
BootMapTable struct to assist with readability in bootmap
entry code. Also:

- replace ScsiMbr in ECKD code with appropriate structs
- fix read_block messages to reflect BootMapTable
- fixup ipl_scsi to use BootMapTable (referred to as Program Table)
- defined value for maximum table entries
Signed-off-by: NCollin L. Walling <walling@linux.vnet.ibm.com>
Reviewed-by: NThomas Huth <thuth@redhat.com>
Acked-by: NChristian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: NThomas Huth <thuth@redhat.com>