flash_ec: Respect the raiden flag if no board given
flash_ec: Respect the raiden flag if no board given

In a lab servo, flash_ec is executed without the board flag. In this
case, don't check the board flag for raiden and simply respect the
raiden flag.

BRANCH=none
BUG=b:38319398
TEST=Ran the flash_ec script in a lab servo.

Change-Id: Ib3757a4b7b550fd77facffdf2009cc3317591888
Reviewed-on: https://chromium-review.googlesource.com/506461
Commit-Ready: Wai-Hong Tam <04b587fdf5845741a0c5a8b9cd59ca72d73ef8fc@google.com>
Tested-by: Wai-Hong Tam <04b587fdf5845741a0c5a8b9cd59ca72d73ef8fc@google.com>
Reviewed-by: Mary Ruthven <81380f3403fed74252e92df3ed012a1819ec6296@chromium.org>

coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec