rtw89: fix potentially access out of range of RF register array

The RF register array is used to help firmware to restore RF settings.
The original code can potentially access out of range, if the size is
between (RTW89_H2C_RF_PAGE_SIZE * RTW89_H2C_RF_PAGE_NUM + 1) to
((RTW89_H2C_RF_PAGE_SIZE + 1) * RTW89_H2C_RF_PAGE_NUM). Fortunately,
current used size doesn't fall into the wrong case, and the size will not
change if we don't update RF parameter.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20211119055729.12826-1-pkshih@realtek.com