kbuild: Make DEBUG_SECTION_MISMATCH selectable, but not on by default

CONFIG_DEBUG_SECTION_MISMATCH has also runtime effects due to the
-fno-inline-functions-called-once compiler flag, so forcing it on
everyone is not a good idea.
Signed-off-by: Michal Marek <mmarek@suse.cz>

lib/Kconfig.debug

@@ -102,7 +102,6 @@ config HEADERS_CHECK
 
 config DEBUG_SECTION_MISMATCH
 	bool "Enable full Section mismatch analysis"
-	default y
 	help
 	  The section mismatch analysis checks if there are illegal
 	  references from one section to another section.