icnss: Change to skip driver remove if shutdown blocked

In idle-restart event handler, shutdown is blocked before
driver op idle_restart is called and the icnss driver state
is updated to ICNSS_BLOCK_SHUTDOWN. On receiving modem
notifier, the driver remove needs to be skipped if shutdown
is already blocked.

Change-Id: I9753eb578374879856e2a5ab7a79f5ea219d0218
Signed-off-by: Mohammed Siddiq <msiddiq@codeaurora.org>