tegra210: change to UTF-8 (from ISO-8859)

Prompted by Phabricator's complaint that a C source file was a binary
file, in D43192.

Reviewed by: mmel
Differential Revision: https://reviews.freebsd.org/D43229

(cherry picked from commit 56c202de785a5701831ae345a1a5c906e0b2c3e6)