wifi: rtw89: coex: Remove trace_step at COEX-MECH control structure for RTL8852C

RTL8852C don't need to send the data trace_step which used to tell
firmware how many TDMA steps should record. Remove the member.

Signed-off-by: Ching-Te Ku <ku920601@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20220913092546.43722-7-pkshih@realtek.com