Make arm64 serial port config compatible with crosvm

BUG: 118442619
Test: Ran ~/bin/crosvm run --disable-sandbox ~/image, saw output
Change-Id: If086af28b69eca5353a101228ae986653bc1465e
Signed-off-by: Greg Hartman <ghartman@google.com>
(cherry picked from commit 2860dfe869a94c8c1950effb55da116f83ebc740)
1 file changed