flash_ec: remove hammer like boards from BOARDS_STM32 array
flash_ec: remove hammer like boards from BOARDS_STM32 array

flash_ec script is able to infer chip name from servod, we don't
need this explicit list for hammer.

BUG=none
TEST=flash ec command `util/flash_ec --board zed` still works
BRANCH=main

Signed-off-by: Ting Shen <c671d3efec3d7e7e285f3788bf0d1ba4c8605b78@google.com>
Change-Id: I4f4d72aa3f30e6178f6f7a968af6e2bc8a5c7845
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2807250
Commit-Queue: Ting Shen <c671d3efec3d7e7e285f3788bf0d1ba4c8605b78@chromium.org>
Tested-by: Ting Shen <c671d3efec3d7e7e285f3788bf0d1ba4c8605b78@chromium.org>
Reviewed-by: Chen-Tsung Hsieh <77554e79ae3cd4c7dffb45bb74e91a0ebfd68cd4@chromium.org>
Reviewed-by: Eric Yilun Lin <2f2733c7206ea2b76bd2db1905cc5e8a75841c48@chromium.org>

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