stm32mon: fix unable to flash to nyan board problem
stm32mon: fix unable to flash to nyan board problem

When comparing chip name of "STM32L15", use strncmp to compare the
first 8 characters.

BUG=chrome-os-partner:34558
BRANCH=none
TEST=flash_ec --board nyan

Signed-off-by: Yen Lin <yelin@nvidia.com>
Reviewed-on: https://chromium-review.googlesource.com/235511
Reviewed-by: Vincent Palatin <vpalatin@chromium.org>
Reviewed-by: Gwendal Grignou <gwendal@chromium.org>
(cherry picked from commit 589836638254829fbb765b0d679b0e27d121c3fa)
Signed-off-by: Duncan Laurie <70662b43bc1a20b57ded72a2b08be88dd0da4841@chromium.org>

Change-Id: I3318385cee1d4e4c4d9688591f7a7bfd46c54dee
Reviewed-on: https://chromium-review.googlesource.com/236348
Tested-by: Duncan Laurie <70662b43bc1a20b57ded72a2b08be88dd0da4841@chromium.org>
Trybot-Ready: Duncan Laurie <70662b43bc1a20b57ded72a2b08be88dd0da4841@chromium.org>
Reviewed-by: Duncan Laurie <70662b43bc1a20b57ded72a2b08be88dd0da4841@chromium.org>
Commit-Queue: Duncan Laurie <70662b43bc1a20b57ded72a2b08be88dd0da4841@chromium.org>

thehobn/ec,thehobn/ec,thehobn/ec,thehobn/ec