ibmvnic: Flush existing work items before device removal

ibmvnic: Flush existing work items before device removal

[ Upstream commit 6954a9e4192b86d778fb52b525fd7b62d51b1147 ]

Ensure that all scheduled work items have completed before continuing
with device removal and after further event scheduling has been
halted. This patch fixes a bug where a scheduled driver reset event
is processed following device removal.

Signed-off-by: Thomas Falcon <tlfalcon@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>