ath10k: fix potential memory leak in ath10k_wmi_tlv_op_pull_fw_stats()

ath10k_wmi_tlv_op_pull_fw_stats() uses tb = ath10k_wmi_tlv_parse_alloc(...)
function, which allocates memory. If any of the three error-paths are
taken, this tb needs to be freed.

Signed-off-by: Christian Lamparter <chunkeey@googlemail.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>