rtw88: fill zeros to words 0x06 and 0x07 of security cam entry

8723D adds some experimental features to word 0x06 of cam entry, so fill
zeros to initialize them to off state. For existing chips, these two words
are reserved and always zeros, so this change is harmless for them.

Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Yan-Hsuan Chuang <yhchuang@realtek.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200512102621.5148-9-yhchuang@realtek.com