Revert "gnu: u-boot: Update to 2020.10."

This reverts commit fe6067fc24.  This commit
broke u-boot-tools.

gnu/packages/bootloaders.scm

@@ -446,7 +446,7 @@ (define-public dtc
 (define u-boot
   (package
     (name "u-boot")
-    (version "2020.10")
+    (version "2020.07")
     (source (origin
               (method url-fetch)
               (uri (string-append
@@ -454,7 +454,7 @@ (define u-boot
                     "u-boot-" version ".tar.bz2"))
               (sha256
                (base32
-                "08m6f1bh4pdcqbxf983qdb66ccd5vak5cbzc114yf3jwq2yinj0d"))))
+                "0sjzy262x93aaqd6z24ziaq19xjjjk5f577ivf768vmvwsgbzxf1"))))
     (native-inputs
      `(("bc" ,bc)
        ("bison" ,bison)

gnu/packages/patches/u-boot-riscv64-fix-extlinux.patch

@@ -32,9 +32,9 @@ Index: u-boot/configs/sifive_fu540_defconfig
 ===================================================================
 --- u-boot.orig/configs/sifive_fu540_defconfig
 +++ u-boot/configs/sifive_fu540_defconfig
-@@ -27,3 +27,5 @@ CONFIG_SPL_DM_SEQ_ALIAS=y
- CONFIG_SPL_CLK=y
+@@ -12,3 +12,5 @@ CONFIG_DISPLAY_BOARDINFO=y
+ CONFIG_DEFAULT_DEVICE_TREE="hifive-unleashed-a00"
+ CONFIG_SYS_RELOC_GD_ENV_ADDR=y
  CONFIG_DM_MTD=y
- CONFIG_DM_RESET=y
 +CONFIG_USE_PREBOOT=y
 +CONFIG_PREBOOT="setenv fdt_addr ${fdtcontroladdr}; fdt addr ${fdtcontroladdr};"