rtlwifi: rtl8188ee: remove redundant assignment of variable rtlpriv->btcoexist.reg_bt_sco

Assigning value "3" to "rtlpriv->btcoexist.reg_bt_sco" here, but that
stored value is overwritten before it can be used.

Coverity reports this problem as
CWE563: A value assigned to a variable is never used.
drivers/net/wireless/realtek/rtlwifi/rtl8188ee/hw.c:
rtl8188ee_bt_reg_init

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/1617182023-110950-1-git-send-email-yang.lee@linux.alibaba.com