rtlwifi: Rework rtl_lps_leave() and rtl_lps_enter() to use work queue

In commit a5ffbe0a, some of the calls to rtl_lps_leave() were switched
to be called from a work queue to avoid a scheduling while atomic bug.
This patch converts the remaining calls to use the work queue. In
addition, the call to rtl_lps_enter() is also switched to the work
queue. None of these newly converted calls had triggered the bug (yet),
but this change make all of them fit a single pattern.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Cc: jcheung@suse.com
Cc: machen@suse.com
Cc: mmarek@suse.cz
Cc: zhiyuan_yang@realsil.com.cn
Cc: page_he@realsil.com.cn
Signed-off-by: John W. Linville <linville@tuxdriver.com>