NOTES: Tidy entries for SATA controllers

• Add typical comments after device entries (copied from amd64 GENERIC)

• Add an entry for 'device ada'. Normally this is pulled in via 'device sd', but is documented in ada(4) and can be used to include ATA/SATA disk support in a kernel without SCSI disk support.

Reviewed by: imp
Sponsored by: Chelsio Communications
Differential Revision: https://reviews.freebsd.org/D44689

(cherry picked from commit a508f5d92a93cda11b0c68084dbb181f97e7f5f7)