u-boot-duovero: Remove port

This has been marked as BROKEN for a long time now.

u-boot-*: Remove U_BOOT_SLAVE_PORTREVISION_2021.04

This is not needed anymore as we have 2921.07 now.

sysutils/u-boot-*: Remove ubldr support

We have been using loader.efi on armv7 for a long time now.
Remove support for booting with ubldr and the needed patches that were
never upstreamed.
While here add CONFIG_EFI_GRUB_ARM32_WORKAROUND=y in the Fragment as it's
needed to have the cache flushed for us when loader.efi is started.

One more small cleanup, forgotten yesterday.
Reported by:	lwhsu

Remove # $FreeBSD$ from Makefiles.

sysutils/u-boot: Update to 2020.04

While here use python3 for it as it now works.
Two slave ports have been marked broken :
u-boot-pandaboard and u-boot-duovero
Both of those boards have ~0 users in FreeBSD so if you are one of
those raise your hand.

Use HTTPS as possible

Clean up trailing spaces

Approved by:	manu
Sponsored by:	The FreeBSD Foundation

Consolidate maintainership of various u-boot ports under u-boot@.

Submitted by:		manu
Differential Revision:	D15884

Update the instruction and description of the u-boot ports which use
u-boot-master.

Submitted by:		manu
Differential Revision:	D15883

Use the correct config file name for duovero and pandaboard

Approved by:	imp

Roll forward to u-boot v2017.01. Many thanks to manu@ for cleaning up
our patches to u-boot and getting them upstreamed.

Future commits will roll other families over to this as testing on
them is completed.

Remove the files added as a stupid workaround for git svn.

Convert duovero over to u-boot-master.

Fix hardcoded package description path

Submitted by:	mat

Fix few style violations in u-boot ports:

- GMAKE -> MAKE_CMD, MAKE_CMD is always set to required make implementation
- CP -> INSTALL_DATA, INSTALL_DATA makes sure files are always installed
  with proper permissions
- sysutils/u-boot-rpi: include missed files installed in STAGEDIR in PLIST_FILES

PR:		210982
Submitted by:	myself
Approved by:	maintainers timeout

Remove ${PORTSDIR}/ from dependencies, categories r, s, t, and u.

With hat:	portmgr
Sponsored by:	Absolight

Remove trailing whitespace from Makefiles, M-X.

Use gcc 4.9.2 to cross-compile u-boot for duovero.

Approved by:	rpaulo

Add a U-Boot port for the Duovero system.

PR:		196488
Submitted by:	Scott Ellis
Approved by:	bapt