MFC 339952:

Approved by: bcr (mentor)
Differential Revision: https://reviews.freebsd.org/D24054

tpm(4): Add the STANDARDS and HISTORY sections

Also, link to the homepage of the BSSSD project, which developed the
original driver.

Reviewed by: bcr, kevans
Approved by: krion (mentor, implicit), mat (mentor, implicit)
Differential Revision: https://reviews.freebsd.org/D17608