msm: npu: Fix race condition issue when disabling fw

npu_disable_fw_work may be queued multiple times in certain race
contition, so it may call disable fw function multiple times by
mistake. A condition check is added to only allow it to disable fw
if it's enabled by itself to fix this issue.

Change-Id: Ia3c7136b3bd575fff016100f400638f98dfb6835
Signed-off-by: Jilai Wang <jilaiw@codeaurora.org>