soc/mediatek/mt8188: Remove the GPIO setting of USB1_DRV_VBUS

USB1_DRV_VBUS is used to provide 5V power for USB on MT8188 EVB and it's
not used on Geralt. Therefore, remove the GPIO setting of USB1_DRV_VBUS.

TEST=read usb data successfully.
BUG=b:236331724

Change-Id: Iffea7b288c83c81648d4c7ca30d2f0961f9853ff
Signed-off-by: Liju-Clr Chen <liju-clr.chen@mediatek.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/72641
Reviewed-by: Rex-BC Chen <rex-bc.chen@mediatek.com>
Reviewed-by: Yidi Lin <yidilin@google.com>
Reviewed-by: Yu-Ping Wu <yupingso@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/soc/mediatek/mt8188/usb.c

@@ -14,7 +14,4 @@
 void mtk_usb_prepare(void)
 {
 	mt_pll_set_usb_clock();
-
-	/* usb drvvbus for 5v power */
-	gpio_output(GPIO(USB1_DRV_VBUS), 1);
 }