Add a crypto capability flag for accelerated software drivers.

[jhb]

Summary

Use this in GELI to print out a different message when accelerated
software such as AESNI is used vs plain software crypto.

While here, simplify the logic a bit for determing which type of
crypto driver was chosen the first time by examining the capabilities
of the matched driver after a single call to crypto_newsession rather
than making separate calls with different flags.

Test Plan

• created a temporary geli (geli onetime) on a memory disk (md0) with only cryptosoft present, with aesni.ko loaded, and with ccr0 present and verify the string printed by GELI for all three cases

[jhb]

sys/geom/eli/g_eli.c

989 ↗

(On Diff #72651)

"hardware" may also not be quite the right name. Something like "co-processor" might be more apt? However, were we to do that, it would also make sense I think to have a little helper method shared by this function and the XML dumping code that maps the sc_crypto value to a string.

[delphij]

LGTM.

(I don't think I have any better idea on the wording of 'hardware' either, maybe leave it as-is for now?)