nvme_ahci: Mark AHCI devices as such in the controller

Add a quirk to flag AHCI attachment to the controller. This is for any
of the strategies for attaching nvme devices as children of the AHCI
device for Intel's RAID devices. This also has a side effect of cleaning
up resource allocation from failed nvme_attach calls now.

Sponsored by: Netflix
Reviewed by: mav
Differential Revision: https://reviews.freebsd.org/D33285

(cherry picked from commit 7cf8d63c884c484fee9b287f792549ee15270ae7)