ideapad: fix software rfkill setting

This fixes a several year old regression that I found while trying
to get the Yoga 3 11 to work. The ideapad_rfk_set function is meant
to send a command to the embedded controller through ACPI, but
as of c1f73658, it sends the index of the rfkill device instead
of the command, and ignores the opcode field.

This changes it back to the original behavior, which indeed
flips the rfkill state as seen in the debugfs interface.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: c1f73658 ("ideapad: pass ideapad_priv as argument (part 2)")
Cc: stable@vger.kernel.org # v2.6.38+
Signed-off-by: Darren Hart <dvhart@linux.intel.com>