stm32: fixed spi shared_mem_release bug
stm32: fixed spi shared_mem_release bug

If shared_mem_acquire() failed, we should not call shared_mem_release().

BRANCH=none
BUG=chrome-os-partner:34703
TEST="Compiled"

Signed-off-by: Sheng-Liang Song <ssl@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/236392
Reviewed-by: David Hendricks <dhendrix@chromium.org>
Reviewed-by: Alexandru Stan <amstan@chromium.org>
Reviewed-by: Randall Spangler <rspangler@chromium.org>
(cherry picked from commit 005fa5fea19f406a76eeed50084ae86d38c8de85)
Signed-off-by: Duncan Laurie <70662b43bc1a20b57ded72a2b08be88dd0da4841@chromium.org>

Change-Id: I5179f8b75b13451a63eb3209c9156066231aa12d
Reviewed-on: https://chromium-review.googlesource.com/237116
Tested-by: Duncan Laurie <70662b43bc1a20b57ded72a2b08be88dd0da4841@chromium.org>
Commit-Queue: Duncan Laurie <70662b43bc1a20b57ded72a2b08be88dd0da4841@chromium.org>
Trybot-Ready: Duncan Laurie <70662b43bc1a20b57ded72a2b08be88dd0da4841@chromium.org>
Reviewed-by: Duncan Laurie <70662b43bc1a20b57ded72a2b08be88dd0da4841@chromium.org>

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