arm-bsp/u-boot: remove old 2020.04 recipe

This was only used by Corstone 700, so is redundant now.

Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Jon Mason <jon.mason@arm.com>

meta-arm-bsp/recipes-bsp/u-boot/u-boot_2020.04.bb

@@ -1,28 +0,0 @@
-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 = "36fec02b1f90b92cf51ec531564f9284eae27ab4"
-
-SRC_URI = "git://git.denx.de/u-boot.git;branch=master \
-          "
-
-S = "${WORKDIR}/git"
-B = "${WORKDIR}/build"
-do_configure[cleandirs] = "${B}"
-
-require recipes-bsp/u-boot/u-boot.inc
-
-DEPENDS += "bc-native dtc-native"