Make martinkr@ owner of //device/fido/mac.

Bug: None
Change-Id: Ibc16a2c01d1611e44613a0c80b80afb0954183e1
Reviewed-on: https://chromium-review.googlesource.com/1174532
Commit-Queue: Balazs Engedy <engedy@chromium.org>
Reviewed-by: Martin Kreichgauer <martinkr@chromium.org>
Reviewed-by: Balazs Engedy <engedy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#583017}

device/fido/mac/OWNERS

+martinkr@chromium.org
+martinkr@google.com
+
+# TEAM: security-dev@chromium.org
+# COMPONENT: Blink>WebAuthentication