wcn36xx: Correct remove bss key response encoding

The WCN36XX_HAL_RMV_BSSKEY_RSP carries a single u32 with "status", so we
can use the standard status check function for decoding the result.

This is the last user of the v2 status checker, so remove the struct and
helper function.

Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>