uboot-rockchip: fix RockPro64 boot from eMMC

With upstream commit f81f9f0ebac5 ("rockchip: rockpro64: initialize USB in
preboot") CONFIG_USE_PREBOOT was enabled on the RockPro64, which is causing
boot issues when a eMMC is used, as a workaround will temporarily disable
this option.

Signed-off-by: Marty Jones <mj8263788@gmail.com>
[Improve patch description]
Signed-off-by: David Bauer <mail@david-bauer.net>

package/boot/uboot-rockchip/patches/101-rock64pro-disable-CONFIG_USE_PREBOOT.patch

+From 2114d68b3c755ec8043ae9e43ac8e9753e0cec84 Mon Sep 17 00:00:00 2001
+From: Marty Jones <mj8263788@gmail.com>
+Date: Sun, 17 Jan 2021 15:26:09 -0500
+Subject: [PATCH] rockpro64: disable CONFIG_USE_PREBOOT
+
+On commit https://github.com/u-boot/u-boot/commit/f81f9f0ebac596bae7f27db095f4f0272b606cc3
+CONFIG_USE_PREBOOT was enabled on the RockPro64.
+
+When the board is booting, U-Boot hangs as soon as it disables the USB
+controller. This is a workaround until a final solution is deployed
+upstream.
+
+Signed-off-by: Marty Jones <mj8263788@gmail.com>
+---
+ configs/rockpro64-rk3399_defconfig | 1 -
+ 1 file changed, 1 deletion(-)
+
+--- a/configs/rockpro64-rk3399_defconfig
++++ b/configs/rockpro64-rk3399_defconfig
+@@ -12,7 +12,6 @@ CONFIG_SPL_SPI_FLASH_SUPPORT=y
+ CONFIG_SPL_SPI_SUPPORT=y
+ CONFIG_DEFAULT_DEVICE_TREE="rk3399-rockpro64"
+ CONFIG_DEBUG_UART=y
+-CONFIG_USE_PREBOOT=y
+ CONFIG_DEFAULT_FDT_FILE="rockchip/rk3399-rockpro64.dtb"
+ CONFIG_DISPLAY_BOARDINFO_LATE=y
+ CONFIG_MISC_INIT_R=y