Add qat(4)

This provides an OpenCrypto driver for Intel QuickAssist devices. The
driver was initially ported from NetBSD and comes with a few
improvements:

• support for GMAC/AES-GCM, AES-CTR and AES-XTS, and support for SHA/HMAC-authenticated encryption
• support for detaching the driver
• various bug fixes
• DH895X support

Discussed with: jhb
MFC after: 3 days
Sponsored by: Rubicon Communications, LLC (Netgate)
Differential Revision: https://reviews.freebsd.org/D26963