Update blake2 accelerated software tests to work after OCF refactoring.

Update blake2 accelerated software tests to work after OCF refactoring.

- Lookup device drivers to test by name instead of assuming that the
  software / hardware flags will select specific drivers.
- Set the sysctl to permit software /dev/crypto requests when testing
  the accelerated software blake2 driver.

PR:		245825
Reported by:	lwhsu
Reviewed by:	cem, lwhsu
Sponsored by:	Chelsio Communications
Differential Revision:	https://reviews.freebsd.org/D24540