brcmfmac: fix returning cipher_suite for get_key operation.

brcmfmac: fix returning cipher_suite for get_key operation.

When multiple cipher suites have been programmed then the lowest
suite is to be retured. This fixes issue when AP mode is using
CCMP and TKIP WPA combination where rekeying will fail.

Reviewed-by: Arend Van Spriel <arend@broadcom.com>
Reviewed-by: Pieter-Paul Giesberts <pieterpg@broadcom.com>
Reviewed-by: Piotr Haber <phaber@broadcom.com>
Signed-off-by: Hante Meuleman <meuleman@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>