futility: Prefer debug header servo over CCD when both are available.

BRANCH=none
BUG=b:270287312
TEST=With atlas DUT + servo_v4p1 + cr50_ccd + servo_micro:

$ dut-control -o servo_type  # servo_v4p1_with_servo_micro_and_ccd_cr50
$ dut-control cpu_fw_spi  # unknown value but control does exist
$ dut-control ccd_cpu_fw_spi  # error from control not existing
$ futility read --servo -v ap-fw.bin  # succeeds

With atlas DUT + servo_micro:

$ dut-control -o servo_type  # servo_micro
$ dut-control cpu_fw_spi  # unknown value but control does exist
$ dut-control ccd_cpu_fw_spi  # error from control not existing
$ futility read --servo -v ap-fw.bin  # succeeds

With atlas DUT + servo_v4p1 + cr50_ccd:

$ dut-control -o servo_type  # servo_v4p1_with_ccd_cr50
$ dut-control ccd_cpu_fw_spi  # off
$ futility read --servo -v ap-fw.bin  # succeeds

Change-Id: I18e890aaa6c3fa63f2108840b8c344a6adc5a561
Signed-off-by: Matthew Blecker <matthewb@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/4315198
Reviewed-by: Hung-Te Lin <hungte@chromium.org>
Reviewed-by: Edward O'Callaghan <quasisec@chromium.org>