dts: pulldown GPIO7_B5(BT_POWER_EN) to enable BT_PCM_OUT

Change-Id: I57ee7020840daa6a1ec8b6ff4f04112aed51ec78
Signed-off-by: Rock Shen <rock_shen@asus.com>

Author: RockShen-ASUS

arch/arm/boot/dts/rk3288-tinker_board.dts

@@ -961,6 +961,7 @@
 	gpio_init_config {
 		gpio_init: gpio-init {
                         rockchip,pins =
+				<7 13 RK_FUNC_GPIO &pcfg_pull_down>,
 				<7 22 RK_FUNC_GPIO &pcfg_pull_none>,
 				<7 23 RK_FUNC_GPIO &pcfg_pull_none>;
 		};