libfdt: Fix invalid version warning

python does not like the u-boot- prefix in the version, drop it.

/usr/lib/python3.10/site-packages/setuptools/dist.py:544: UserWarning:
The version specified ('u-boot-2022.10') is an invalid version, this may
not work as expected with newer versions of setuptools, pip, and PyPI.
Please see PEP 440 for more details.

Signed-off-by: Michal Suchanek <msuchanek@suse.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/scripts/dtc/pylibfdt/Makefile b/scripts/dtc/pylibfdt/Makefile
index 493995e..a7579f0 100644
--- a/scripts/dtc/pylibfdt/Makefile
+++ b/scripts/dtc/pylibfdt/Makefile
@@ -17,7 +17,7 @@
       cmd_pymod = unset CROSS_COMPILE; unset CFLAGS; \
 		CC="$(HOSTCC)" LDSHARED="$(HOSTCC) -shared " \
 		LDFLAGS="$(HOSTLDFLAGS)" \
-		VERSION="u-boot-$(UBOOTVERSION)" \
+		VERSION="$(UBOOTVERSION)" \
 		CPPFLAGS="$(HOSTCFLAGS) -I$(LIBFDT_srcdir)" OBJDIR=$(obj) \
 		SOURCES="$(PYLIBFDT_srcs)" \
 		SWIG_OPTS="-I$(LIBFDT_srcdir) -I$(LIBFDT_srcdir)/.." \