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>
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 8b6a4f1..5a24805 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -102,7 +102,6 @@
 
 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.