rtl8xxxu: Add REG_DWBCN1_CTRL_8723B define

List yet another new register found on the 8723b.
Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_regs.h

@@ -397,6 +397,8 @@
 #define REG_AUTO_LLT			0x0224
 #define  AUTO_LLT_INIT_LLT		BIT(16)
 
+#define REG_DWBCN1_CTRL_8723B		0x0228
+
 /* 0x0280 ~ 0x02FF	RXDMA Configuration */
 #define REG_RXDMA_AGG_PG_TH		0x0280
 #define  RXDMA_USB_AGG_ENABLE		BIT(31)