ath10k: handle 10.4 fw wmi ready event

Reuse existing function ath10k_wmi_op_pull_rdy_ev()
to parse WMI_10_4_READY_EVENTID and handle the same
event in ath10k_wmi_10_4_op_rx().

Signed-off-by: Raja Mani <rmani@qti.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>