scsi: Forceably finish migration to DM_SCSI

scsi: Forceably finish migration to DM_SCSI

The migration deadline for moving to DM_SCSI was v2023.04. A further
reminder was sent out in August 2023 to the remaining platforms that had
not migrated already, and that a few more over the line (or configs
deleted).

With this commit we:
- Rename CONFIG_DM_SCSI to CONFIG_SCSI.
- Remove all of the non-DM SCSI code. This includes removing other
  legacy symbols and code and removes some legacy non-DM AHCI code.
- Some platforms that had previously been DM_SCSI=y && SCSI=n are now
  fully migrated to DM_SCSI as a few corner cases in the code assumed
  DM_SCSI=y meant SCSI=y.

Signed-off-by: Tom Rini <trini@konsulko.com>