Support AF_ALG crypto in Linux

Hi,

These days all AMD CPUs have a on-board Crypotographic CoProcessor 
(CCP), which is part of the Platform Security Processor (PSP). It has 
hardware encryption and decryption as well as a randnr generator. In 
current Kernels, the CCP is available throuh AF_ALG interface.

I do not think that GnuTLS supports this. Doing a web search I found 
only one reference to a 2 year old patch: 
https://gitlab.com/gnutls/gnutls/-/issues/308

IMHO it would be great if GnuTLS would consider adding support for this. 
On my AMD Athlon 3000G, OpenSSL generated almost 30x performance 
increase with AF_ALG enabled!

Relevant kernel doc: 
https://www.kernel.org/doc/html/v5.7/crypto/userspace-if.html

Anders