rtlwifi: Remove extra workqueue for enter/leave power state

rtlwifi: Remove extra workqueue for enter/leave power state

When the rtlwifi family of drivers was converted to use a workqueue when
entering or leaving power save mode (commits 75c8edb1d9, d7a4f824fb,
b8229d38c0, d94c04a7e2, and 54b6e5fa82), the code began scheduling work from
the callback routine of a different workqueue with a resulting increase in
overhead.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>