wifi: rtw89: 8922a: set memory heap address for secure firmware

Secure firmware is protected by public/private key cryptography. To help
firmware self verify integrity, configure a heap address for these
data before downloading firmware.

Signed-off-by: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20230901073956.54203-9-pkshih@realtek.com