util/flash_ec: Fix shellcheck warnings
util/flash_ec: Fix shellcheck warnings

if $(in_array "${BOARDS_SPI_1800MV[@]}" "${BOARD}"); then
   ^-- SC2091: Remove surrounding $() to avoid executing output (or use
               eval if intentional).

BRANCH=none
BUG=b:242127759
TEST=./util/flash_ec --board=dartmonkey

Signed-off-by: Tom Hughes <fc5c12f30a5ed2baa0581f44ee14ad1eb7b20d83@chromium.org>
Change-Id: Id13d83d65f6b95a320830251d391d6ae65e9c497
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3858399
Reviewed-by: Andrea Grandi <f017805e76e0e7a74072a3bac1b6e29e65eedeab@google.com>

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