Disable unused pylibfdt

The `imply BINMAN` causes `pylibfdt` to be built, which requires python. We
don't currently expose `pylibfdt`, or declare python dependencies, so disable
it.

diff -ur a/arch/Kconfig b/arch/Kconfig
--- a/arch/Kconfig	2023-01-09 09:07:33.000000000 -0700
+++ b/arch/Kconfig	2023-08-11 14:01:05.998403114 -0600
@@ -205,7 +205,6 @@
 	imply KEYBOARD
 	imply PHYSMEM
 	imply GENERATE_ACPI_TABLE
-	imply BINMAN
 
 config SH
 	bool "SuperH architecture"