scripts: Rename build-efi.py to drop the file extension

The .py extension isn't very useful. Drop it and update the shebang to
specify Python 3

Update the docs for this and also drop the old reference to 2021 images.

Signed-off-by: Simon Glass <sjg@chromium.org>

MAINTAINERS

@@ -1074,7 +1074,7 @@ F:	doc/develop/uefi/u-boot_on_efi.rst
 F:	drivers/block/efi-media-uclass.c
 F:	drivers/block/sb_efi_media.c
 F:	lib/efi/
-F:	scripts/build-efi.py
+F:	scripts/build-efi
 F:	test/dm/efi_media.c
 
 EFI LOGGING

doc/develop/uefi/u-boot_on_efi.rst

@@ -97,9 +97,8 @@ that EFI does not support booting a 64-bit application from a 32-bit
 EFI (or vice versa). Also it will often fail to print an error message if
 you get this wrong.
 
-You may find the script `scripts/build-efi.py` helpful for building and testing
-U-Boot on UEFI on QEMU. It also includes links to UEFI binaries dating from
-2021.
+You may find the script `scripts/build-efi` helpful for building and testing
+U-Boot on UEFI on QEMU.
 
 See `Example run`_ for an example run.
 
@@ -202,7 +201,7 @@ Example run
 
 This shows running with serial enabled (see `include/configs/efi-x86_app.h`)::
 
-   $ scripts/build-efi.py -wsPr
+   $ scripts/build-efi -wsPr
    Packaging efi-x86_app32
    Running qemu-system-i386
 

scripts/build-efi

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # SPDX-License-Identifier: GPL-2.0+
 """
 Script to build an EFI thing suitable for booting with QEMU, possibly running