scsi: scsi_debug: Add environmental reporting log subpage

Log subpages are starting to appear in real devices (e.g. SSDs) so add
support for one. Adopt approach where all "wild" sub-pages are themselves
listed as long as there is at least one non-wild page or subpage for a
given page number.

Link: https://lore.kernel.org/r/20220109012853.301953-10-dgilbert@interlog.com


Signed-off-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>