x86: edison: Switch to DM_USB_GADGET

DM is the modern default approach for the drivers in U-Boot.
It also allows to configure code via Device Tree.

Move Intel Edison to use DM_USB_GADGET and drop hard coded values.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/configs/edison_defconfig b/configs/edison_defconfig
index ab2811e..304a172 100644
--- a/configs/edison_defconfig
+++ b/configs/edison_defconfig
@@ -37,6 +37,7 @@
 CONFIG_DFU_MMC=y
 CONFIG_DFU_RAM=y
 CONFIG_SUPPORT_EMMC_BOOT=y
+CONFIG_DM_USB_GADGET=y
 CONFIG_USB_GADGET=y
 CONFIG_USB_GADGET_MANUFACTURER="Intel"
 CONFIG_USB_GADGET_VENDOR_NUM=0x8087