Add support for Intel Atom S1200 UART

PR: 278316

Signed-off-by: Henrich Hartzer <henrichhartzer@tuta.io>
Reviewed by: imp
Pull Request: https://github.com/freebsd/freebsd-src/pull/1164
(cherry picked from commit 1f2776e123603042944aad9f41ceb46b5b28d8ae)