rtlwifi: Fix logic error in enter/exit power-save mode

In commit a269913c ("rtlwifi: Rework rtl_lps_leave() and
rtl_lps_enter() to use work queue"), the tests for enter/exit
power-save mode were inverted. With this change applied, the
wifi connection becomes much more stable.

Fixes: a269913c ("rtlwifi: Rework rtl_lps_leave() and rtl_lps_enter() to use work queue")
Signed-off-by: Wang YanQing <udknight@gmail.com>
CC: Stable <stable@vger.kernel.org> [3.10+]
Acked-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>