wifi: rtw89: cleanup unused rtwdev::roc_work

The needed one was moved to rtwvif::roc_work. And, rtwdev::roc_work is
unused. So, remove it.

Signed-off-by: Zong-Zhe Yang <kevin_yang@realtek.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Link: https://patch.msgid.link/20250120034004.21135-1-pkshih@realtek.com