rtlwifi: use work for lps

rtlwifi: use work for lps

Leaving leisure power save mode can take some time, so it's better to
perform that action in process context with interrupts enabled. This
patch changes lps_leave tasklet to work.

Reported-by: Philipp Dreimann <[email protected]>
Tested-by: Larry Finger <[email protected]>
Cc: Mike McCormack <[email protected]>
Cc: Chaoming Li <[email protected]>
Signed-off-by: Stanislaw Gruszka <[email protected]>
Signed-off-by: Larry Finger <[email protected]>
Signed-off-by: John W. Linville <[email protected]>