payloads/U-Boot: Use github mirror and latest version

Update the U-Boot version to the latest release. Also switch to github
since it is typically much faster to download than the existing URL.

Drop the 'experimental' tag since this payload is pretty stable. It is
also tested regularly in U-Boot's CI.

Change-Id: I082130539c3474593a82e4b21cb995380f4db168
Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/77149
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/77463
Reviewed-by: Patrick Georgi <patrick@coreboot.org>
Tested-by: Patrick Georgi <patrick@coreboot.org>
Reviewed-by: Elyes Haouas <ehaouas@noos.fr>
diff --git a/payloads/external/U-Boot/Kconfig.name b/payloads/external/U-Boot/Kconfig.name
index fbef16e..5f24280 100644
--- a/payloads/external/U-Boot/Kconfig.name
+++ b/payloads/external/U-Boot/Kconfig.name
@@ -1,5 +1,5 @@
 config PAYLOAD_UBOOT
-	bool "U-Boot (Experimental)"
+	bool "U-Boot"
 	depends on ARCH_X86
 	help
 	  Select this option if you want to build a coreboot image
diff --git a/payloads/external/U-Boot/Makefile b/payloads/external/U-Boot/Makefile
index c29fe2b..ea850b3 100644
--- a/payloads/external/U-Boot/Makefile
+++ b/payloads/external/U-Boot/Makefile
@@ -5,7 +5,7 @@
 
 project_name=U-Boot
 project_dir=u-boot
-project_git_repo=http://git.denx.de/u-boot.git
+project_git_repo=http://github.com/u-boot/u-boot/
 project_build_dir=build
 project_config_file=$(project_build_dir)/.config