poplar_defconfig: enable fastboot support

It enables fastboot support on Poplar board by using DWC2 OTG gadget
driver.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
diff --git a/configs/poplar_defconfig b/configs/poplar_defconfig
index 239783a..ea0ea89 100644
--- a/configs/poplar_defconfig
+++ b/configs/poplar_defconfig
@@ -11,11 +11,22 @@
 # CONFIG_ISO_PARTITION is not set
 CONFIG_DEFAULT_DEVICE_TREE="hi3798cv200-poplar"
 CONFIG_ENV_IS_IN_MMC=y
+CONFIG_USB_FUNCTION_FASTBOOT=y
+CONFIG_FASTBOOT_BUF_ADDR=0x20000000
+CONFIG_FASTBOOT_BUF_SIZE=0x10000000
+CONFIG_FASTBOOT_FLASH=y
+CONFIG_FASTBOOT_FLASH_MMC_DEV=0
 CONFIG_MMC_DW=y
 CONFIG_MMC_DW_K3=y
 CONFIG_USB=y
 CONFIG_USB_EHCI_HCD=y
 CONFIG_USB_EHCI_GENERIC=y
+CONFIG_USB_GADGET=y
+CONFIG_USB_GADGET_MANUFACTURER="HiSilicon"
+CONFIG_USB_GADGET_VENDOR_NUM=0x18d1
+CONFIG_USB_GADGET_PRODUCT_NUM=0xd00d
+CONFIG_USB_GADGET_DWC2_OTG=y
+CONFIG_USB_GADGET_DWC2_OTG_PHY_BUS_WIDTH_8=y
 CONFIG_USB_HOST_ETHER=y
 CONFIG_USB_ETHER_ASIX=y
 CONFIG_FAT_WRITE=y