rtlwifi: rtl8821ae: Fix connection lost problem

In commit 40b368af ("rtlwifi: Fix alignment issues"), the read
of REG_DBI_READ was changed from 16 to 8 bits. For unknown reasonsi
this change results in reduced stability for the wireless connection.
This regression was located using bisection.

Fixes: 40b368af

 ("rtlwifi: Fix alignment issues")
Reported-and-tested-by: James Cameron <quozl@laptop.org>
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Stable <stable@vger.kernel.org> # 4.11+
Cc: Ping-Ke Shih <pkshih@realtek.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>