modpost: fix section mismatch check for exported init/exit sections

Since commit f02e8a6596 ("module: Sort exported symbols"),
EXPORT_SYMBOL* is placed in the individual section ___ksymtab(_gpl)+<sym>
(3 leading underscores instead of 2).

Since then, modpost cannot detect the bad combination of EXPORT_SYMBOL
and __init/__exit.

Fix the .fromsec field.

Fixes: f02e8a6596 ("module: Sort exported symbols")
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

scripts/mod/modpost.c

@@ -980,7 +980,7 @@ static const struct sectioncheck sectioncheck[] = {
 },
 /* Do not export init/exit functions or data */
 {
-	.fromsec = { "__ksymtab*", NULL },
+	.fromsec = { "___ksymtab*", NULL },
 	.bad_tosec = { INIT_SECTIONS, EXIT_SECTIONS, NULL },
 	.mismatch = EXPORT_TO_INIT_EXIT,
 	.symbol_white_list = { DEFAULT_SYMBOL_WHITE_LIST, NULL },