qtnfmac: convert "Append IEs" command to QTN_TLV_ID_IE_SET usage

Data contained within "Append IEs" command (QLINK_CMD_MGMT_SET_APPIE)
duplicates QTN_TLV_ID_IE_SET TLV. Convert the command to use that TLV
instead.

Signed-off-by: Igor Mitsyanko <igor.mitsyanko.os@quantenna.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>