acer-wmi: fix rfkill conversion

"rfkill: rewrite" incorrectly reversed
the meaning of 'state' in acer_rfkill_update() when it changed
rfkill_force_state() to rfkill_set_sw_state().  Fix it.

Signed-off-by: Troy Moure <twmoure@szypr.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>