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

FLASHROM_OPTIONS="-i EC_RW -i WP_RO -l "${L}" --noverify-all"
					^--^ SC2027: The surrounding
					quotes actually unquote this.
					Remove or escape them.

${FLASHROM_WRITE} -w "${T}" \
^---------------^ SC2086: Double quote to prevent globbing and word
                  splitting.

${FLASHROM_CMDLINE} -r "${FLAGS_read}" \
^-----------------^ SC2086: Double quote to prevent globbing and word
                    splitting

Convert the variable to an array to split on spaces correctly:
https://github.com/koalaman/shellcheck/wiki/Sc2086#exceptions.

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

Signed-off-by: Tom Hughes <fc5c12f30a5ed2baa0581f44ee14ad1eb7b20d83@chromium.org>
Change-Id: Iac286c110c770eeb70a92002fb59c214f1ca648c
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3860073
Reviewed-by: Bobby Casey <a3c107f0b4efaee07148ab0813ba992bba562a69@google.com>

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