ath10k: Fix memory leak in qmi

Currently the memory allocated for qmi handle is
not being freed during de-init which leads to memory leak.

Free the allocated qmi memory in qmi deinit
to avoid memory leak.

Tested HW: WCN3990
Tested FW: WLAN.HL.3.1-01040-QCAHLSWMTPLZ-1

Fixes: fda6fee0001e ("ath10k: add QMI message handshake for wcn3990 client")
Signed-off-by: Dundi Raviteja <dundi@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>