arm-bsp: create u-boot 2020.07 to resolve warning

Poky, etc master branches updated the u-boot recipes to use 2020.10,
causing bbappends for 2020.07 to no longer function.  Create a temporary
recipe for 2020.07 until all the BSPs can update to support the latest
version.

Change-Id: Ib5fc9b8a2ff2ccf01be3640a34429d2c1e57b627
Signed-off-by: Jon Mason <jon.mason@arm.com>

meta-arm-bsp/recipes-bsp/u-boot/u-boot_2020.07.bb

@@ -0,0 +1,28 @@
+HOMEPAGE = "http://www.denx.de/wiki/U-Boot/WebHome"
+DESCRIPTION = "U-Boot, a boot loader for Embedded boards based on PowerPC, \
+ARM, MIPS and several other processors, which can be installed in a boot \
+ROM and used to initialize and test the hardware or to download and run \
+application code."
+SECTION = "bootloaders"
+DEPENDS += "flex-native bison-native"
+
+COMPATIBLE_MACHINE = "(corstone700-*)"
+
+LICENSE = "GPLv2+"
+LIC_FILES_CHKSUM = "file://Licenses/README;md5=30503fd321432fc713238f582193b78e"
+PE = "1"
+
+# We use the revision in order to avoid having to fetch it from the
+# repo during parse
+SRCREV = "2f5fbb5b39f7b67044dda5c35e4a4b31685a3109"
+
+SRC_URI = "git://git.denx.de/u-boot.git \
+          "
+
+S = "${WORKDIR}/git"
+B = "${WORKDIR}/build"
+do_configure[cleandirs] = "${B}"
+
+require recipes-bsp/u-boot/u-boot.inc
+
+DEPENDS += "bc-native dtc-native"