[PATCH] doc: fix build with sphinx 5.0 and later.

[Quentin Schulz]

From: Quentin Schulz <quentin.schulz at theobroma-systems.com>

Sphinx 5.0 and later fails to build when language is set to None:
Warning, treated as error:
Invalid configuration value found: 'language = None'. Update your configuration to a valid langauge code. Falling back to 'en' (English)

Let's set the language to English since it is the language used for the
documentation.

Cc: Quentin Schulz <foss+uboot at 0leil.net>
Signed-off-by: Quentin Schulz <quentin.schulz at theobroma-systems.com>
---
Cc: u-boot at lists.denx.de
---
 doc/conf.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/doc/conf.py b/doc/conf.py
index eac3accd56..62c8d31270 100644
--- a/doc/conf.py
+++ b/doc/conf.py
@@ -178,7 +178,7 @@ finally:
 #
 # This is also used if you do content translation via gettext catalogs.
 # Usually you set "language" from the command line for these cases.
-language = None
+language = 'en'
 
 # There are two options for replacing |today|: either, you set today to some
 # non-false value, then it is used:

---
base-commit: d25b11ae9f10a7455fb16680ac2e0e573d02c79e
change-id: 20221107-upstream-sphinx-5-language-3a3f21715614

Best regards,
-- 
Quentin Schulz <quentin.schulz at theobroma-systems.com>