rtlwifi: rtl8723be: fix duplicated code for different branches

Refactor code in order to avoid identical code for different branches.

Addresses-Coverity-ID: 1248728
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Acked-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>