ath10k: fix tracing build for ath10k_wmi_cmd

Commit be8b3943 ("ath10k: make WMI commands block by design") broke
the build if CONFIG_ATH10K_TRACING was enabled.

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>