ath10k: fix possible memory leak in ath10k_bmi_lz_data_large()

'cmd' is malloced in ath10k_bmi_lz_data_large() and should be freed
before leaving from the error handling cases, otherwise it will cause
memory leak.

Fixes: d58f466a

 ("ath10k: add large size for BMI download data for SDIO")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200427104348.13570-1-weiyongjun1@huawei.com