flash_ec: Look for flashrom in PATH before /usr/sbin
flash_ec: Look for flashrom in PATH before /usr/sbin

/usr/sbin should have lower priority than $PATH.

This allows pointing to a different version of flashrom by setting the
path variable.

It shouldn't have any impact because by default flashrom is installed in
/usr/sbin.

BUG=none
BRANCH=none
TEST=PATH=/tmp/zork:$PATH flash_ec --board=zork --image=foo.bin

Change-Id: Ie656bec10145734bdec1f067b08f164afcf89e90
Signed-off-by: Raul E Rangel <9a9c998e11a2655b1de9a05eeeef5f710c0dc7ed@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/1842034
Commit-Queue: Edward Hill <db1406b34e091703092b6b136bdfeb2c8125fc0e@chromium.org>
Reviewed-by: Edward Hill <db1406b34e091703092b6b136bdfeb2c8125fc0e@chromium.org>

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