wcn36xx: Use correct command struct for EXIT_BMPS_REQ

EXIT_BMPS_REQ was using the command struct for ENTER_BMPS_REQ. I
spotted this when looking at command dumps.

Signed-off-by: Pontus Fuchs <pontus.fuchs@gmail.com>
Merge pull request #143 from pof2/exit_bmps

wcn36xx: Use correct command struct for EXIT_BMPS_REQ