arm-bsp: convert general u-boot bbappend to version specific

The generic u-boot bbappend is causing issues upstream when trying to
use new or older versions of u-boot, by trying to apply patches from
folders that do not exist.

Change-Id: I399e3234fba852382fc73ab68f14a7e826bb5a42
Signed-off-by: Jon Mason <jon.mason@arm.com>

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

@@ -0,0 +1,8 @@
+#
+# Corstone700 KMACHINE
+#
+FILESEXTRAPATHS_prepend_corstone700 := "${THISDIR}/${BP}/corstone700:"
+SRC_URI_append_corstone700 = " file://0001-arm-Add-corstone700-platform.patch \
+                               file://0002-boot-add-bootx-command-to-start-XiP-images.patch \
+                               file://0003-boot-starting-the-XIP-kernel-using-bootx-command.patch \
+                               file://0004-arm-enabling-the-arch_timer-driver.patch"

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

@@ -35,13 +35,3 @@ SRC_URI_append_juno = " file://u-boot_vexpress_uenv.patch"
 # Total Compute KMACHINE
 #
 SRC_URI_append_tc0 = " file://0001-Add-support-for-Total-Compute.patch"
-
-#
-# Corstone700 KMACHINE
-#
-FILESEXTRAPATHS_prepend_corstone700 := "${THISDIR}/files/corstone700:"
- 
-SRC_URI_append_corstone700 = " file://0001-arm-Add-corstone700-platform.patch \
-                               file://0002-boot-add-bootx-command-to-start-XiP-images.patch \
-                               file://0003-boot-starting-the-XIP-kernel-using-bootx-command.patch \
-                               file://0004-arm-enabling-the-arch_timer-driver.patch"