kbuild: remove CONFIG_HAVE_UNDERSCORE_SYMBOL_PREFIX

CONFIG_HAVE_UNDERSCORE_SYMBOL_PREFIX was selected by BLACKFIN, METAG.
They were removed by commit 4ba66a9760 ("arch: remove blackfin port"),
commit bb6fb6dfcc ("metag: Remove arch/metag/"), respectively.

No more architecture enables CONFIG_HAVE_UNDERSCORE_SYMBOL_PREFIX.
Clean up the rest of scripts, and remove the Kconfig entry.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>

scripts/adjust_autoksyms.sh

@@ -61,9 +61,6 @@ for mod in "$MODVERDIR"/*.mod; do
 	sed -n -e '3{s/ /\n/g;/^$/!p;}' "$mod"
 done | sort -u |
 while read sym; do
-	if [ -n "$CONFIG_HAVE_UNDERSCORE_SYMBOL_PREFIX" ]; then
-		sym="${sym#_}"
-	fi
 	echo "#define __KSYM_${sym} 1"
 done >> "$new_ksyms_file"